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TEK MULTI-PURPOSEOSCILLOSCOPES

OSCILLOSCOPEPRIMER

THE XYZsOF USING A SCOPE

Tektronix COMMITTED TO EXCELLENCE

CONTENTS

INTRODUCTION 1 PART II. Making Measurements 19

PART I. Scopes, Controls, & Probes 2 Chapter 6. WAVEFORMS 19

Chapter 1. THE DISPLAY SYSTEMBeam FinderIntensityFocusTrace RotationUsing the Display Controls

Chapter 7. SAFETY 22

Chapter 8. GETTING STARTEDCompensating the ProbeChecking the ControlsHandling Probe

22222222

Chapter 2. THE VERTICAL SYSTEMVertical PositionInput CouplingVertical SensitivityVariable VOLTS/DIVChannel 2 InversionVertical Operating ModesAlternate Sweep SeparationUsing the Vertical Controls

Chapter 9. MEASUREMENT TECHNIQUESThe Foundations: Amplitude and Time MeasurementsFrequency and Other Derived MeasurementsPulse MeasurementsPhase MeasurementsX-Y MeasurementsUsing the Z-Axis

Chapter 3. THE HORIZONTAL SYSTEMHorizontal PositionHorizontal Operating ModesSweep SpeedsVariable SEC/DIVHorizontal MagnificationThe DELAY TIME and MULTIPLIER ControlsThe B DELAY TIME POSITION ControlUsing the Horizontal Controls

Using TV TriggeringDelayed Sweep Measurements

Single Time Base ScopesDual Time Base Scopes

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REPRODUCED BY PERMISSIONOF THE COPYRIGHT OWNER:TEKTRONIX, INC.(Letter dated: 11/20/85,Gaithersbucp, Md.)

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Chapter 10. SCOPE PERFORMANCESquare Wave Response and High Frequency ResponseInstrument Rise Time and Measured Rise TimesBandwidth and Rise Time

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Chapter 4. THE TRIGGER SYSTEMTrigger Level and SlopeVariable Trigger HoldoffTrigger SourcesTrigger Operating ModesTrigger CouplingUsing the Trigger Controls

Chapter 5. ALL ABOUT PROBESCircuit LoadingMeasurement System BandwidthProbe TypesPicking a Probe

Copyright @ 1981, Tektronix, Inc All rights reserved

INTRODUCTION

If you watch an electrical en-gineer tackling a tough designproject, or a service engineertroubleshooting a stubbornproblem, you’ll see them grab ascope, fit probes or cables, andstart turning knobs and settingswitches without ever seemingto glance at the front panel. Tothese experienced users, theoscilloscope is their most impor-tant tool but their minds are fo-cused on solving the problem,not on using the scope.

Making oscilloscope mea-surements is second nature tothem. It can be for you too, butbefore you can duplicate theease with which they use ascope, you will need to concen-trate on learning about thescope itself: both how it worksand how to make it work for you.

The purpose of this primer isto help you learn enough aboutoscilloscopes and oscilloscopemeasurements that you will beable to use these measurementtools quickly, easily, and accu-rately.

The text is divided into twoparts:

The first four chapters of Part Idescribe the functional parts ofscopes and the controls asso-ciated with those parts. Then achapter on probes concludesthe section.

Part II allows you to build onthe knowledge and experienceyou gained from Part I. The sig-nals you’ll see on the screen ofan oscilloscope are identified bywaveshape and the terms forparts of waveforms are dis-cussed. The next two chapterscover safety topics and instru-ment set-up procedures.

Then Chapter 9 describesmeasurement techniques.Exercises there let you practicesome basic measurements, andseveral examples of advancedtechniques that can help youmake more accurate and con-venient measurements are alsoincluded. The last chapter in thisprimer discusses oscilloscope

performance and its effects onyour measurements.

Having a scope in front of youwhile working through the chap-ters is the best way to both learnand practice applying your newknowledge. While the funda-mentals will apply to almost anyscope, the exercises and illus-trations use two specific instru-ments: the Tektronix 2213 and2215 Portable Oscilloscopes.The 2213 is a dual-channel, 60MHz portable designed as aneasy-to-use, lightweight,general-purpose oscilloscope.The 2215 is a dual time baseoscilloscope with more featuresand capabilities; it’s included soyou will understand dual timebase scopes and appreciatethe additional measurementcapabilities they offer.

If you have comments orquestions about the material inthis primer, please don’t hesitateto write.Chet HeybergerPortable Scopes TechnicalCommunications ManagerMarshall E. Pryor2200 Series Product LineMarketing ManagerPrimer - DS 391199Tektronix, Inc.PO. Box 500Beaverton, OR 97077

PART I. SCOPES, CONTROLS, & PROBES

You can measure almost any-thing with the two-dimensionalgraph drawn by an oscillo-scope. In most applications thescope shows you a graph ofvoltage (on the vertical axis)versus time (on the horizontalaxis). This general-purposedisplay presents far more infor-mation than is available fromother test and measurement in-struments like frequency coun-ters or multimeters. For exam-ple, with a scope you can findout how much of a signal is di-rect, how much is alternating,how much is noise (and whetheror not the noise is changing withtime), and what the frequency ofthe signal is as well. Using ascope lets you see everything atonce rather than requiring you tomake many separate tests.

Most electrical signals can beeasily connected to the scopewith either probes or cables.And then for measuring non-electrical phenomena, trans-ducers are available. Transduc-ers change one kind of energyinto another. Speakers andmicrophones are two examples;the first changes electrical en-ergy to sound waves and thesecond converts sound intoelectricity. Other typical trans-ducers can transform tempera-ture, mechanical stress, pres-sure, light, or heat into electricalsignals. You can see that giventhe proper transducer, your testand measurement capabilitiesare almost endless with an oscil-loscope.

Making measurements iseasier if you understand thebasics of how a scope works.You can think of the instrument interms of the functional blocks il-lustrated in Figure 1: vertical sys-tern, trigger system, horizontalsystem, and display system.

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VfZgWALSECTION

Figure 1.THE BASIC OSCILLOSCOPE in its most general form has only four functional blocks:vertical, horizontal, trigger, and display systems (and sometimes, sections). Thedisplay system is also sometimes called the CRT (for cathode-ray tube) section.

Each is named for its function.The vertical system controls thevertical axis of the graph; any-time the electron beam thatdraws the graph moves up ordown, it does so under control ofthe vertical system. The horizon-tal system controls the left toright movement of the beam.The trigger system determineswhen the oscilloscope draws; ittriggers the beginning of thehorizontal sweep across thescreen. And the display systemcontains the cathode-ray tube,where the graph is drawn.

This part of the primer is di-vided into chapters for each ofthose functional blocks. Thecontrols for each block arenamed first, and you can use a

two-page, fold-out illustration ofa Tektronix 2213 front panel atthe back of the primer to locatethem on your scope. Next thecontrols and their functions aredescribed, and at the end ofeach chapter there are hands-on exercises using those con-trols.

The last chapter in this sectiondescribes probes. When youfinish reading these five chap-ters, you’ll be ready to make fastand accurate oscilloscopemeasurements.

But before you turn on yourscope, remember that youshould always be careful whenyou work with electrical equip-ment. Observe a// safety pre-cautions in your test and mea-surement operations. Always

plug the power cord of thescope into a properly-wired re-ceptacle before connectingyour probes or turning on thescope; use the proper powercord for your scope, and useonly the correct fuse. Don’t re-move the covers and panels ofyour scope.

Now fold out the front panelillustration at the back of theprimer, so that it is visible as youread. Use the foldout and followExercise 1 to initialize (set instandard positions) the scopecontrols. These standard set-tings are necessary so that asyou follow the directions onthese pages, you’ll see thesame thing on your scope’s CRTas is pictured or described here.

PART I

Exercise 1. INITIALIZING THE SCOPE

Use the foldout figure and call-outs to locate the controls men-tioned here.1. DISPLAY SYSTEM CON-TROLS: Set the AUTO INTEN-SITY control at midrange (abouthalfway from either stop). Turnthe AUTO FOCUS knob com-pletely clockwise.2. VERTICAL SYSTEM CON-TROLS: Turn the channel 7 PO-SITION control completelycounterclockwise. Make surethe lefthand VERTICAL MODEswitch is set to CH 7. Move bothchannel VOLTS/D/V switches tothe least sensitive setting byrotating them completely coun-terclockwise. And make surethe center, red VAR controls arelocked in their detents at the ex-treme clockwise position. Inputcoupling switches should be setto GND.

3. HORIZONTAL SYSTEMCONTROLS: Make sure theHORIZONTAL MODE switch isset to NO DLY for no delay. (Ifyou ’re using a 2275, move theswitch to the A sweep position.)Rotate the SEC/DIV switch to0.5 millisecond (0.5 ms). Makesure the red VAR (variable)switch in the center of the knobis in its detent position by mov-ing it completely clockwise. Andpush in on the VAR switch tomake sure the scope is not in amagnified mode.4. TRIGGER SYSTEM CON-TROLS: Make sure the VARHOLDOFF controlis set to its fullcounterclockwise position. Setthe trigger MODE switch (2275:A TRIGGER MODE) on AUTO.And move the trigger SOURCEswitch (A SOURCE on a 2275) to/NT (internal) and the INT selec-tion switch (A&B INT on a 2275)to CH 7.

After following the steps inExercise 7, you should plug yourscope into a properly-groundedoutlet and turn it on. With a Tek-tronix 2200 scope, there ’s noneed to change the scope'spower supply settings to matchthe local power line; the scopesoperate on main power from 90to 250 Vat at 48 to 62 Hz.

CHAPTER 1. THE DISPLAY SYSTEM

The oscilloscope draws a graph the path of the beam. A grid ofby moving an electron beam lines etched on the inside of theacross a phosphor coating on faceplate serves as the refer-the inside of the CRT (cathode- ence for your measurements;ray tube). The result is a glow for this is the graticule shown ina short time afterward tracing Figure 2.

CENTERGWTICUE

I LINES -

Figure 2.THE GRATICLJLE is a grid of lines typically etched or silk-screened on the inside ofthe CRT faceplate. Putting the graticule inside-on the same plane as the tracedrawn by the electron beam. and not on the outside of the glass - eliminatesmeasurement inaccuracies called parallax errors. Parallax errors occur when thetrace and the graticule are on different planes and the observer is shifted slightly fromthe direct line of sight. Though different sized CRT’s may be used, graticules areusually laid out in an 8 x 10 pattern. Each of the eight vertical and ten horizontal linesblock off major divisions (or just divisions) of the screen. The labeling on scopecontrols always refers to major divisions. The tick marks on the center graticule linesrepresent minor divisions or subdivisions. Since rise time measurements are verycommon. 2200 Series scope graticules include rise time measurement markings:dashed lines for 0 and 100% points, and labeled graticule lines for 10 and 90%

Common controls for displaysystems include intensity andfocus; less often, you will alsofind beam finder and trace rota-tion controls. On a Tektronix2200 Series instrument they areall present, grouped next to andon the right of the CRT At the topof the group is the intensity con-trol (labeled AUTO INTENSITYon a 2200 because these in-struments automatically main-tain the trace intensity once it isset). The TRACE ROTATION ad-justment is under that, and thenthe beam finder (BEAM FIND).Under the probe adjustmentjack is the focus control (labeledAUTO FOCUS because it’s alsoautomatic). The functions ofthese controls are describedbelow and their positions on theTektronix 2213 Portable Oscillo-scope are illustrated by the fold-out illustration at the rear of thebooklet.

Beam FinderThe beam finder is a conven-ience control that allows you tolocate the electron beam any-time it’s off-screen. When youpush the BEAM FIND button,you reduce the vertical andhorizontal deflection voltages(more about deflection voltageslater) and over-ride the intensitycontrol so that the beam alwaysappears within the 8 x 10-centimeter screen. When yousee which quadrant of thescreen the beam appears in,you’ll know which directions toturn the horizontal and verticalPOSITION controls to repositionthe trace on the screen for nor-mal operations.

IntensityAn intensity control adjusts thebrightness of the trace. It’snecessary because you use ascope in different ambient lightconditions and with many kindsof signals. For instance, onsquare waves you might want tochange the trace brightness tolook at different parts of thewaveform because the slowerhorizontal components will al-ways appear brighter than thefaster vertical components.

Intensity controls are also use-ful because the intensity of atrace is a function of both howbright the beam is and how longit’s on-screen. As you select dif-ferent sweep speeds (a sweepis one movement of the electronbeam across the scope screen)with the SEC/DIV switch, thebeam ON and OFF timeschange and the beam has moreor less time to excite the phos-phor

On most scopes, you have toturn the intensity up or down torestore the initial brightness. Onthe 2200 Series scopes, how-ever the automatic intensity cir-cuit compensates for changesin sweep speed from 0.5 milli-seconds (0.5 ms) to 0.5 micro-seconds (0.5 ,us). Within thisrange, the automatic circuitmaintains the same trace inten-sity you initially set with theAUTO INTENSITY control.

FocusThe scope’s electron beam isfocused on the CRT faceplateby an electrical grid within thetube. The focus control adjuststhat grid for optimum tracefocus. On a 2200 scope, theAUTO FOCUS circuit maintainsyour focus settings over mostintensity settings (0.5 ms to0.5 us).

PART I

Trace RotationAnother display control you’llfind on the front panel of a 2200Series instrument is TRACE RO-TATION. The trace rotation ad-justment allows you to electri-cally align the horizontal deflec-tion of the trace with the fixedgraticule. To avoid accidentalmisalignments when the scopeis in use, the control is recessedand must be adjusted with asmall screwdriver.

If this seems like a calibrationitem that should be adjustedonce and then forgotten, you’reright; that’s true for most oscillo-scope applications. But theearth’s magnetic field affectsthe trace alignment and when ascope is used in many differentpositions - as a service scopewill be - it’s very handy to havea front panel trace rotation ad-justment.

Using the Display ControlsThe display system and its con-trols are shown as functionalblocks in Figure 3. Use Exercise2 to review the display controls.

Figure 3.THE DISPLAY SYSTEM of your scopeconsists of the cathode-ray tube and itscontrols. To draw the graph of your mea-surements, the vertical system of thescope supplies the Y, or vertical, coordi-nates and the horizontal systemsupplies the X coordinates. There is alsoa Z dimension in a scope; it determineswhether or not the electron beam isturned on, and how bright it is when it’son.

l-x---/Exercise 2. THE DISPLAY SYSTEM CONTROLS

and use them as you follow

In Exercise 7 you initialized your

these instructions.

scope and turned on the power.

1. BEAM FIND: Locate theposi-tion of the electron beam bypushing and holding in the

Now you can find the display

BEAM FIND button; then use the

system controls labeled on the

channel 7 vertical POSITIONknob to position the trace on the

foldout front panel illustration

center horizontal graticule line.Keep BEAM FIND depressedand use the horizontal POSI-TION control to center the trace.Release the beam finder.

3. AUTO INTENSITY Set the

2. AUTO FOCUS: The trace you

brightness at a level you like,4. Vertical POSITION: Now you

have on the screen now should

can use the vertical POSITIONcontrol to line up the trace with

be out of focus. Make it as sharp

the first major division line abovethe center of the graticule.

as possible with the AUTO

5. TRACE ROTATION: Use asmall screwdriver and the

FOCUS control.

TRACE ROTATION control to ro-tate the trace in both directions.When you finish, align the traceparallel to the horizontal divisionline closest to it. (After settingthe trace rotation, you may have

to use the vertical POSITIONcontrol again to align the traceon the graticule line.)

You have used all the scope’sdisplay sys tern controls. If at theend of one of these chaptersyou’re not going to go on imme-diately, be sure to turn yourscope off.

5

CHAPTER 2. THE VERTICAL SYSTEM

The vertical system of yourscope supplies the display sys-tem with the Y axis - or vertical- information for the graph onthe CRT screen. To do this, thevertical system takes the inputsignals and develops deflectionvoltages. The display systemthen uses the deflection volt-ages to control - deflect-theelectron beam.

The vertical system also givesyou a choice of how you connectthe input signals (called cou-pling and described below).And the vertical system pro-vides internal signals for thetrigger circuit (described inChapter 4). Figure 4 illustratesthe vertical system schemati-cally.

Some of the vertical systemcontrols - see the foldout frontpanel illustration for their loca-tions - are: vertical position,sensitivity, and input coupling.

Because all 2200s are two-channel scopes, you will haveone set of these switches foreach channel. There are alsotwo switches for choosing thescope’s vertical display modeand one control that allows youto invert the polarity of the chan-nel 2 signal.

For the exercises in this chap-ter, you’ll need a 10X probe likethe Tektronix P6120 10X Probessupplied with every 2200 Seriesscope.

Vertical PositionYour scope’s POSITION controlslet you place the trace exactlywhere you want it on the screen.The two vertical POSITION con-trols (there’s one for each chan-nel) change the vertical place-ment of the traces from eachvertical channel; the horizontalPOSITION control changes thehorizontal position of bothchannels at once.

Input CouplingThe input coupling switch foreach vertical channel lets youcontrol how the input signal iscoupled to the vertical channel.DC (the abbreviation normallystands for direct current) inputcoupling lets you see all of aninput signal. AC (alternating cur-rent) coupling blocks the con-stant signal components andpermits only the alternatingcomponents of the input signalto reach the channel. An illustra-tion of the differences is shownin Figure 5.

The middle position of thecoupling switches is markedGND for ground. Choosing thisposition disconnects the inputsignal from the vertical systemand makes a triggered displayshow the scope’s chassisground. The position of the traceon the screen in this mode is theground reference level. Switch-ing from AC or DC to GND and

back is a handy way to measuresignal voltage levels with re-spect to chassis ground. (Usingthe GND position does notground the signal in the circuityou’re probing.)

Vertical SensitivityA volts/division rotary switchcontrols the sensitivity of eachvertical channel. Having differ-ent sensitivities extends therange of the scope’s applica-tions; with a VOLTS/DIV switch,a multipurpose scope is capa-ble of accurately displaying sig-nal levels from millivolts to manyvolts.

Using the volts/divisionswitch to change sensitivity alsochanges the scale factor, thevalue of each major division onthe screen. Each setting of thecontrol knob is marked with anumber that represents thescale factor for that channel. Forexample, with a setting of 10 V,

“L- N’lENJAl~

Figure 4.THE VERTICAL SYSTEM of a Tektronix 2200 Series scope consists of two identicalchannels though only one is shown in the drawing. Each channel has circuits tocouple an input signal to that channel, attenuate (reduce) the input signal whennecessary, preamplify it, delay it, and finally amplify the signal for use by the displaysystem. The delay line lets you see the beginning of a waveform even when thescope is triggering on it.

6

PART I

each of the eight vertical majordivisions represents 10 volts andthe entire screen can show 80volts from bottom to top. With aVOLTSDIV setting of 2 milli-volts, the screen can display 16mV from top to bottom.

If you pronounce the "/ ” inVOLTS/DIV as “per” when youread the setting, then you’ll re-member the setting is a scalefactor; for example, read a 20mV setting as “20 millivolts perdivision."

The probe you use influencesthe scale factor. Note that thereare two unshaded areas underthe skirts of the VOLTSDIVswitches. The right-hand areashows the scale factor when youuse the standard 1 OX probe. Theleft area shows the factor for a IXprobe.

Variable VOLTS/DIVThe red VAR (for variable) con-trol in the center of the VOLTS/DIV switch provides a continu-ously variable change in thescale factor to a maximumgreater than 2.5 times theVOLTS/DIV setting.

A variable sensitivity control isuseful when you want to makequick amplitude comparisonson a series of signals. You could,for example, take a known sig-nal of almost any amplitude anduse the VAR control to makesure the waveform fits exactly onmajor division graticule lines.Then as you used the same ver-tical channel to look at other sig-nals, you could quickly seewhether or not the later signalshad the same amplitude.

Channel 2 InversionTo make differential measure-ments (described in Part II), youhave to invert the polarity of oneof your input channels. The IN-VERT control on the verticalamplifier for channel 2 providesthis facility. When you push it in,the signal on channel 2 is in-verted. When the switch is out,both channels have the samepolarity.

Figure 5.VERTICAL CHANNEL INPUT COUPLING CONTROLS let you choose AC and DCinput coupling and ground. DC coupling connects the entire input signal to thevertical channel. AC coupling blocks constant signal components and only con-nects alternating components to the vertical channel. The GND position disconnectsthe input signal and shows you the scope’s chassis ground level. AC coupling ishandy when the entire signal (alternating plus constant components) might be toolarge for the VOLTSDIV switch settings you want. In a case like this, you might seesomething like the first photo. But eliminating the direct component allows you to lookat the alternating signal with a VOLTSDIV setting that is more convenient as in thesecond photo.

Vertical Operating ModesScopes are more useful if theyhave more than one vertical dis-play mode, and with your Tek-tronix 2200, you have severalcontrolled by two VERTICALMODE switches: channel 1alone; channel 2 alone; bothchannels in either the alternateor chopped mode; and bothchannels algebraicallysummed.

To make the scope displayonly channel 1, use the CH 1 po-sition on the left-hand switch.

To display only channel 2, usethe CH 2 position on the left-hand switch.

To see both channels in thealternate vertical mode, movethe left-hand switch to BOTH(which enables the right-handswitch) and then move theright-hand switch to ALT Nowyou can see both channelssince the signals are drawn al-ternately. The scope completes

a sweep on channel 1, then asweep on channel 2, and so on.

To display both channels inthe chop mode, you move theleft-hand switch to BOTH andthe right-hand one to CHOP Inthe chop mode, the scopedraws small parts of both sig-nals by switching back and forthat a fast fixed rate while youreyes fill in the gaps.

THE VERTICAL SYSTEM CONT.

Both chop and alternate areprovided so that you can look attwo signals at any sweep speed.The alternate mode draws firstone trace and then the other, butnot both at the same time. Thisworks great at the faster sweepspeeds when your eyes can’tsee the alternating. To see twosignals at the slower sweeps,you need the chop mode.

If you want to see the two inputsignals combined into onewaveform on the screen, useBOTH on the left-hand and ADDon the right-hand switch. Thisgives you an algebraically-combined signal: either channel1 and 2 added, (CH 1) + (CH 2);or channel 1 minus channel 2when channel 2 is inverted,(+CH 1) + (-CH 2).

Alternate Sweep SeparationOn the 2215 dual time basescope, there is also a sweepseparation control: A/B SWPSEP. It’s used to change the po-sition of the scope’s B sweeptraces with respect to the Asweeps. Using the A/B sweepseparation in conjunction withthe vertical POSITION controlslets you place all four traces (twochannels and two time bases)on the screen so that they don’toverlap. (Dual time base scopemeasurements are described inChapter 9.)

Figure 6.THE TEKTRONIX P6120 10X PROBE connects to the BNC connector of either chan-nel 1 (shown) or 2; unlike the photo, the probe’s ground strap is usually connected tothe ground of the circuit you are working on. The probe adjustment jack is labeledPROBE ADJUST and is located near the CRT controls on the front panel.

Using the Vertical Controls l both VAR VOLTSDIV switches collar of the channel 2 BNCBefore using the vertical system in their detents at the extreme connector as shown in Figure 6.controls, make sure all the con- clockwise position;trols are positioned where you

Use the callouts on the foldout_ l input coupling levers in GND; figure to remind yourself of the

left them at the end of the lastchapter:l AUTO INTENSITY and AUTO

FOCUS set for a bright, crisptrace;

l trigger SOURCE (A SOURCEon the 2215) switch on INT andthe INT (2215: A&B INT) switchon CH 1;

l trigger MODE (2215: A TRIG-GER MODE) switch on AUTO;

l trigger VAR HOLDOFF controlin its extreme counterclock-wise position;

l VERTICAL MODE is CH 1; control locations and follow thel and HORIZONTAL MODE is directions in Exercises 3 to re-

NO DLY (2215 mode is A). view the vertical system con-

Now connect your 10X probe trols.on the channel 1 BNC connectoron the front panel of your scope.(BNC means “bayonet Neill-Concelman”; named for PaulNeill, who developed the NSeries connector at Bell Labs,and Carl Concelman, whodeveloped the C Series con-nector.)

l SEC/DIV (2215: A and BSECDIV) switch to 0.5 ms;

l both channel VOLTSDIVswitches on 100 V (10X probereading);

Put the tip of the probe into thePROBE ADJ jack. Probes comewith an alligator-clip groundstrap that’s used to ground theprobe to the circuit-under-test.Clip the ground lead onto the

8

PART I

Exercise 3. VERTICAL SYSTEM CONTROLS

Compensating Your Probe1. Turn on the scope and movethe CH 7 VOLTS/D/V switchclockwise to 0.5 V; rememberthe P6720 is a 10X probe, so usethe VOLTS/D/V readout to theright.2. Switch the channel 7 inputcoupling to AC.3. If the signal on the screen isn’tsteady, turn the trigger LEVEL (ATRIGGER LEVEL on the 2275)control until the signal stopsmoving and the TRIG’D light ison. (Use the AUTO FOCUS con-trol if you think you can get thesignal sharper, and AUTO IN-TENSITY to adjust the bright-ness .)4. Next, compensate yourprobe. There’s a screwdriver ad-justment on the compensationbox at the base of the probe;turn it until the tops and bottomsof the square wave on thescreen are flat. (There’s more in-formation about probes andcompensation in Chapter 5.)

Controlling Vertical Sensitivity1. The probe adjustment signalis a square wave of approxi-mately 0.5 volts, and the scalefactor for channel 7 is now ahalf-volt per division. At this set-ting every major division on thescreen represents half a volt.Use the channel 7 vertical POSI-TION control to line up the bot-tom edge of the waveform withthe center graticule line. Thetops of the square wave shouldbe just touching the next majordivision line, proving the probeadjustment signal is approxi-mately 0.5 volts. (Note that theprobe adjustment signal is not acritical circuit in the scope; thisis why the square wave is ap-proximately 0.5 volts.)

2. Turn the VOLTS/D/V switchtwo more click stops to the right.The channel 7 scale factor isnow 0.7 volts /division, and thesignal -still half a volt -is nowabout five major divisions inamplitude.3. Turn the VAR VOLTS/D/V con-trol to the left. That will take it outof its calibrated detent positionand let you see its effect, Since itreduces the scale factor 22%~times, the signal should be lessthan two major divisions inamplitude with this control all theway to the left. If it isn’t exactlythat, don’t worry The variablevolts/division controls are usedto compare signals, not makeamplitude measurements, andconsequently the exact range ofvariation isn’t critical. Return thevariable control to its detent.

Coupling The Signal1. Switch your channel 7 inputcoupling to GND and positionthe trace on the Center graticule.Switch back to the AC couplingposition. Note that the waveformis centered on the screen, Movethe CH 7 VOLTS/D/V switchback to 0.5 volts and note thatthe waveform is still centeredaround the zero reference line.2. Switch to DC coupling. Thetop of the probe adjustment sig-nal should be on the centergraticule line and the signalshould reach to the next lowermajor division. Now you can seethe difference between AC andDC coupling. AC couplingblocked the constant part of thesignal and just showed you ahalf-volt, peak-to-peak, squarewave centered on the zero ref-erence you set at the center ofthe screen. But the DC couplingshowed you that the constantcomponent of the square wave

was all negative-going with re-spect to ground, because in DC,all signal components are con-nected to the vertical channel.

The Vertical Mode Controls1. So far you’ve been using yourscope to see what channel 7 cantell you, but that’s only one ofmany possible vertical modes.Look at the trace for channel 2by moving the scope’s left-mostVERTICAL MODE switch to CH2. The input coupling for chan-nel 2 should still be GND at thispoint, so what you’ll see is theground reference line. Line upthis trace with the graticule linesecond from the top of thescreen with the channel2POSITION control.2. Now move the lever on theleft-hand vertical mode switch toBOTH. That lets you pick one ofthe vertical modes controlled bythe right-hand side verticalmode switch; move it to ALTYou’ve just selected the alter-nate vertical mode. In this mode,your scope alternates betweenthe signals on channel 7 and 2,drawing one complete sweepon channel 7 first, and thendrawing a complete sweep onchannel 2. You can see thishappening when you slow downthe sweep speed, so move theSEC/DIV swtich left to 0.7 sec-onds per division. Now you cansee the two dots from the AC-coupled channel 7 move acrossthe screen for one sweep. Thenthe single dot from channel 2 willmove across the screen. Thepoint is that in the alternatemode each channel is drawncompletely before the scopeswitches to the other channel.

3. Turn the SEC/DIV switch backto 0.5 ms and switch to CHOP asyour vertical mode. The displaylooks a lot like the alternatemode, but the way it’s achievedis entirely different. In alternate,you saw that one channel’s sig-nal was completely written be-fore the other started. Whenyou’re looking at slow signalswith your scope, that can be abother because only one traceat a time will be on-screen. In thechop mode, however, the scopeswitches back and forth veryquickly between the two tracesso that a little part of each isdrawn before going on to thenext. When you look at thescreen, both signals seem con-tinuous because the scope is“chopping” back and forth at avery fast rate - approximately250 kHz in the 2200 Series. Youcan see the chopping if you picka very fast sweep speed. Movethe SECIDIV switch to 70 p.Now the display shows brokenlines because of the chopping.CHOP is most useful for slowsweep speeds, and ALT forfaster sweeps.4. Move the SECIDIV switchback to 0.5 ms. There’s onemore verticalmode: ADD. In theadd mode, the two signals arealgebraically summed (eitherCH1 + CH2, or CH1 - CH2 H2when channel 2 is inverted). Tosee it in operation, move theright-hand VERTICAL MODEswitch to ADD. Now you can seethe combined signal roughlyhalfway between where the twoseparate signals were.

CHAPTER 3. THE HORIZONTAL SYSTEM

To draw a graph, your scopeneeds horizontal as well as ver-tical data. The horizontal systemof your scope supplies the sec-ond dimension by providing thedeflection voltages to move theelectron beam horizontally. Andthe horizontal system contains asweep generator which pro-duces a sawtooth waveform, orramp (see Figure 7), that is usedto control the scope’s sweeprates.

It’s the sweep generator thatmakes the unique functions ofthe modern oscilloscope possi-ble. The circuit that made therate of rise in the ramp linear- arefinement pioneered by Tek-tronix- this was one of the mostimportant advances in oscil-Iography. It meant that the hori-zontal beam movement couldbe calibrated directly in units oftime. That advance made it pos-sible for you to measure time be-tween events much more accu-rately on the scope screen.

Because it is calibrated intime, the sweep generator isoften called the time base. It letsyou pick the time units, observ-ing the signal for either veryshort times measured innanoseconds or microseconds,or relatively long times of severalseconds.

Figure 7.THE SAWTOOTH WAVEFORM is a voltage ramp produced by the sweep generator.The rising portion of the waveform is called the ramp; the falling edge is the retrace;and the time between ramps is the holdoff time. The sweep of the electron beamacross the screen of a scope is controlled by the ramp and the return of the beam tothe left side of the screen takes place during the retrace.

The horizontal system con-trols of a Tektronix 2213 scopeare shown in the foldout figure:the horizontal POSlTION controlis near the top of the panel, andthe HORIZONTAL MODE con-trol is below it; the magnificationand variable sweep speed con-trol is a red knob in the center ofthe SEC/DIV switch; at the bot-tom of the column of horizontalsystem controls are the DELAYTIME switch and the delay timeMULTIPLIER. The dual timebase 2215 has two concentricSEC/DIV controls, and a BDELAY TIME POSITION controlinstead of the delay time switchand multiplier. (The scope con-trols that you use to position the.start of a delayed sweep arealso often called delay time mul-tipliers or DTMs.)

Horizontal PositionLike the vertical POSITION con-trols, you use the horizontal PO-SITION control to change the lo-cation of the waveforms on thescreen.

Horizontal Operating ModesSingle time base scopes usu-

ally have only one horizontal op-erating mode, but the 2213offers normal, intensified, ordelayed-sweep operatingmodes. Dual time base scopeslike the 2215 usually let youselect either of two sweeps. TheA sweep is undelayed (like thesweep of a single time base in-strument), while the B sweep isstarted after a delay time. Addi-tionally, some scopes with twotime bases- and the 2215 is anexample again - let you see thetwo sweeps at once: the Asweep intensified by the Bsweep; and the B sweep itself.This is called an alternate hori-zontal operating mode.

Only the normal horizontaloperating mode is used in thesefirst few chapters, so leave yourscope’s HORIZONTAL OPERA-TING MODE switch in NO DLY(no delay) on the 2213 and A (forA sweep only) on the 2215.Chapter 9, in the second sectionof this primer, describes how tomake delayed sweep mea-surements.

Sweep SpeedsThe seconds/division switchlets you select the rate at whichthe beam sweeps across thescreen; changing SEC/DIVswitch settings allows you tolook at longer or shorter timeintervals of the input signal. Likethe vertical system VOLTS/DIVswitch, the control’s markingsrefer to the screen’s scale fac-tors. If the SEC/DIV setting is 1ms, that means that each hori-zontal major division represents1 ms and the total screen willshow you IO ms.

On the 2215, which has twotime bases, there are two SEC/DIV controls. The A sweep offersall the settings described below;the SEC/DIV switch for the de-layed B sweep has settings for0.05 psldiv to 50 ms/div.

PART I

All the instruments of the Tek-tronix 2200 Series offer sweepspeeds from a half-second foreach division to 0.05 us /division. The markings appear-ing on the scopes are:.5s half a second.2s 0.2 second.l s 0.1 second

50 ms 50 milliseconds(0.05 second)





1 ms 1 millisecond(0.001 second)

.5 ms half a millisecond(0.0005 second)

.2 ms 0.2 millisecond(0.0002 second)

.l ms 0.1 millisecond(0.0001 second)

50 I_CS 50 microseconds(0.00005 second)

20 ps 20 microseconds(0.00002 second)




1 ps 1 microsecond(0.000001 second)

.5 ps half a microsecond(0.0000005 second)

.2 ps 0.2 microsecond(0.0000002 second)

.1 ps 0.1 microsecond(0.0000001 second)

.05 ps 0.05 microseconds(0.00000005 second)

Scopes also have an XY set-ting on the SEC/DIV switch formaking the X-Y measurementsdescribed in Chapter 9.

Variable SEC/DIVBesides the calibrated speeds,you can change any sweepspeed by turning the red VARcontrol in the center of theSEC/DIV switch counterclock-wise. This control slows thesweep speed by at least 2.5:1,making the slowest sweep youhave 0.5 seconds x 2.5, or 1.25seconds/division. Rememberthat the detent in the extremeclockwise direction is the cali-brated position.

Horizontal MagnificationMost scopes offer some meansof horizontally magnifying thewaveforms on the screen. Theeffect of magnification is to mul-tiply the sweep speed by theamount of magnification. On2200 Series scopes there is a10X horizontal magnificationthat you engage by pulling outon the red VAR switch. The 10Xhorizontal magnification givesyou a sweep speed ten timesfaster than the SEC/DIV switchsetting; for example, 0.05 psidivision magnified is a very fast5-nanosecond/division sweep.

The 10X magnification is use-ful when you want to look at sig-nals and see details that occurvery closely together in time.

The DELAY TIME andMULTIPLIER ControlsThis switch and dial are used inconjunction with either the in-tensified or delayed-sweephorizontal operating modes inthe 2213. These features are de-scribed later under “DelayedSweep Measurement” inChapter 9.

The B DELAY TIME POSITIONControlThis calibrated IO-turn dial isused to position the beginningof the B sweep relative to the Asweep in a 2215. Its uses aredescribed under “DelayedSweep Measurements” inChapter 9.

Using the Horizontal ControlsAs you can see in Figure 8, thehorizontal system can be di-vided into two functional blocks:the horizontal amplifier and thesweep generator.

Figure 8.HORIZONTAL SYSTEM components include the sweep generator and the horizontal amplifier. The sweep generator produces asawtooth waveform that is processed by the amplifier and applied to the horizontal deflection plates of the CRT The horizontalsystem also provides the Z axis of the scope; the Z axis determines whether or not the electron beam is turned on -and how brightit is when it’s on.

11

THE TRIGGER SYSTEM PART I

Figure 9.TRIGGERING GIVES YOU A STABLE DISPLAY because the same trigger point startsthe sweep each time. Slope and level controls define the trigger points on the triggersignal. When you look at a waveform on the screen, you’re seeing all those sweepsoverlaid into what appears to be one picture.

Instruments like those in theTektronix 2200 Portable Oscillo-scope family offer a variety oftrigger controls. Besides thosealready mentioned, you alsohave controls that determinehow the trigger system operates(trigger operating mode) andhow long the scope waits be-tween triggers (holdoff).

The control positions are illus-trated by the foldout at the endof the primer. All are located onthe far right of the front panel. Onthe 2213, the variable triggerholdoff (VAR HOLDOFF) is at thetop, and immediately below it isthe trigger MODE switch. Belowthat the trigger SLOPE andLEVEL controls are grouped.Then a set of three switches con-

trols the trigger sources and theexternal trigger coupling. At thebottom of the column of triggercontrols is the external triggerinput BNC connector.

On dual time base 2215scopes, there is a slightly differ-ent control panel layout be-cause you can have a separatetrigger for the B sweep.

Trigger Level and SlopeThese controls define the triggerpoint. The SLOPE control de-termines whether the triggerpoint is found on the rising or thefalling edge of a signal. TheLEVEL control determineswhere on that edge the triggerpoint occurs. See Figure IO.

Figure 10.SLOPE AND LEVEL CONTROLS determine where on the trigger signal the triggeractually occurs. The SLOPE control specifies either a positive (also called the risingorpositive-going) edge or on a negative (falling or negative-going) edge. The LEVELcontrol allows you to pick where on the selected edge the trigger event will takeplace.

13

THE TRIGGER SYSTEM CONT.

Variable Trigger HoldoffNot every trigger event can beaccepted as a trigger. The trig-ger system will not recognize atrigger during the sweep or theretrace, and for a short time af-terward called the ho/doffperiod. The retrace, as you re-member from the last chapter, isthe time it takes the electronbeam to return to the left side ofthe screen to start anothersweep. The holdoff period pro-vides additional time beyondthe retrace that is used to ensurethat your display is stable, asillustrated by Figure 11.

Sometimes the normal holdoffperiod isn’t long enough to en-sure that you get a stable dis-play; this possibility exists whenthe trigger signal is a complexwaveform with many possibletrigger points on it. Though thewaveform is repetitive’ a simpletrigger might get you a series ofpatterns on the screen insteadof the same pattern each time.Digital pulse trains are a goodexample; each pulse is verymuch like any other, so there aremany possible trigger points,not all of which result in the samedisplay.

What you need now is someway to control when a triggerpoint is accepted. The variabletrigger holdoff control providesthe capability. (The control is ac-tually part of the horizontal sys-tem - because it adjusts theholdoff time of the sweepgenerator - but its functioninteracts with the trigger con-trols.) Figure 12 diagrams a situ-ation where the variable holdoffis useful.

Trigger SourcesTrigger sources are groupedinto two categories that dependon whether the trigger signal isprovided internally or externally.The source makes no differencein how the trigger circuit oper-ates’ but internal triggering usu-ally means your scope is trigger-ing on the same signal that it is

Figure 11.TRIGGER HOLDOFF TIME ensures valid triggering. In the drawing only the labeledpoints start the display because no trigger can be recognized during the sweep orthe retrace and holdoff period. The retrace and holdoff times are necessary becausethe electron beam must be returned to the left side of the screen after the sweep, andbecause the sweep generator needs reset time. The CRT Z axis is blanked betweensweeps and unblanked during sweeps.

INW-f5l6NA.L

Figure 12.THE VARIABLE HOLDOFF CONTROLlets you make the scope ignore somepotential trigger points. In the example,all the possible trigger points in the inputsignal would result in an unstable dis-play. Changing the holdoff time to makesure that the trigger point appears onthe same pulse in each repetition of theinput signal is the only way to ensure astable waveform.

14

PART I

displaying. That has the obviousadvantage of letting you seewhere you’re triggering.

Two switches on the frontpanel (labeled SOURCE andINT) determine the triggersource. The internal triggeringsources are enabled when youmove the SOURCE lever to INT.In this position, you can triggerthe scope on the signal fromeither channel, or you canswitch to VERT MODE.

Triggering on one of thechannels works just like itsounds: you’ve set the scope totrigger on some part of thewaveform present on thatchannel.

Using the VERTICAL MODEsetting on the internal sourceswitch means that the scope’sVERTICAL MODE switches de-termine what signal is used fortriggering. If the VERTICALMODE switches are set at CH 1,then the signal on channel 1triggers the scope. If you’re look-ing at channel 2, then that chan-nel triggers it. If you switch to thealternate vertical mode, then thescope looks for triggers alter-nately on the two channels. If thevertical mode is ADD, then CH 1 + CH 2 is the triggering signal.And in the CHOP vertical mode,the scope triggers the same asin ADD, which prevents the in-strument from triggering on thechop frequency instead of yoursignals.

You can see that verticalmode triggering is a kind of au-tomatic source selection thatyou can use when you mustswitch back and forth betweenvertical modes to look at differ-ent signals.

But triggering on the dis-played signal isn’t always whatyou need, so external triggeringis also available. It often givesyou more control over the dis-play. To use an external trigger,you set the SOURCE switch toits EXT position and connect thetriggering signal to the BNCconnector marked EXT INPUT

on the front panel. Occasionswhen external triggering is use-ful often occur in digital designand repair; there you might wantto look at a long train of verysimilar pulses while triggeringwith an external clock or with asignal from another part of thecircuit.

The LINE position on theSOURCE switch gives youanother triggering possibility:the power line. Line triggering isuseful anytime you’re looking atcircuits that are dependent onthe power line frequency.Examples include devices likelight dimmers and powersupplies.

These are all the triggersource possibilities on a 2200Series scope:

Switch Positions

Trigger Source

channel 1 onlychannel 2 onlyexternallinevertical mode(either channel1 or 2 or both)

SOURCE INT

INT CH1INT CH2EXT disabledLINE disabledINT VERT MODE

Trigger Operating ModesThe 2200 Series trigger circuitscan operate in four modes: nor-mal, automatic, television, andvertical mode.

One of the most useful is thenormal trigger mode (markedNORM on the MODE switch)because it can handle a widerrange of trigger signals than anyother triggering mode. The nor-mal mode does not permit atrace to be drawn on the screenif there’s no trigger. The normalmode gives you the widestrange of triggering signals: fromDC to 60 MHz.

In the automatic (or “brightbaseline”) mode (labeled AUTOon the front panel): a triggerstarts a sweep; the sweep endsand the holdoff period expires.At that point a timer begins torun; if another trigger isn’t foundbefore the timer runs out, a trig-ger is generated anyway caus-ing the bright baseline to appeareven when there is no waveform

on the channel. In the 2200Series, the automatic mode is asignal-seeking auto mode. Thismeans that for most of the sig-nals you’ll be measuring, theauto mode will match the triggerlevel control to the trigger signal.That makes it most unlikely thatyou will set the trigger level con-trol outside of the signal range.The auto mode lets you triggeron signals with changing volt-age amplitudes or waveshapeswithout making an adjustment ofthe LEVEL control.

Another useful operatingmode is television triggering.Most scopes with this mode letyou trigger on tv fields atsweeps of 100 &division andslower, and tv lines at 50 psldivor faster. With a 2200 Seriesscope, you can trigger on eitherfields or lines at any sweepspeed; for tv field triggering, usethe TV FIELD switch position,and for television line triggering,use the NORM or AUTOsettings.

You’ll probably use the normaland automatic modes the mostoften. The AUTO because it’sessentially totally automatic,and normal because it’s themost versatile. For example, it’spossible to have a low fre-quency signal with a repetitionrate that is mismatched to therun-out of an automatic modetimer; when that happens thesignal will not be steady in theauto mode. Moreover, the auto-matic signal-seeking modecan’t trigger on very low fre-quency trigger signals. Thenormal mode, however, will giveyou a steady signal at any reprate.

The last 2200 Series triggeroperating mode, the verticalmode, is unique in its advan-tages. Selecting the VERTMODE position on the INTswitch automatically selects thetrigger source as you read in“Trigger Source” above. It alsomakes alternate triggering pos-sible. In this operating mode,

the scope triggers alternately onthe two vertical channels. Thatmeans you can look at two com-pletely unrelated signals. Mostscopes only trigger on onechannel or the other when thetwo signals are not synchro-nous.

Here’s a review of the 2200trigger modes:

TriggerOperating Mode Switch Settings

normal NORM on the MODE switchautomatic AUTO on the MODE switchtelevision field TV FIELD on the MODE

switchtelevision line NORM or AUTO on the

MODE switchvertical mode VERT MODE on the INT

switch

15

THE TRIGGER SYSTEM CONT.

Triggering CouplingJust as you may pick either al-ternating or direct couplingwhen you connect an input sig-nal to your scope’s vertical sys-tem, you can select the kind ofcoupling you need when youconnect a trigger signal to thetrigger system’s circuits. Forinternal triggers, the verticalinput coupling selects the trig-ger coupling. For external trig-ger signals, however, you mustselect the coupling you want:

Coupling

DC

Applications

DC couples all elements of thetriggering signal (both AC andDC) to the trigger circuit.

DC with If you want DC coupling andattenuation the external trigger is too large

for the trigger system, movethe TRIGGER COUPLINGswitch to its DC+10 setting.

AC This coupling blocks DCcomponents of the triggersignal and couples only the ACcomponents.

Using the Trigger ControlsTo review what you’ve learnedabout the trigger circuit and itscontrols (shown schematicallyin Figure 13), first make sure allyour controls are in these posi-tions:

l 0.5 VOLTS/DIV on channel 1and VAR in its detent position;

l AC vertical coupling;l CH 1 on the VERTICAL MODE

switch;l 0.5 ms sweep speed and no

magnification or variableSEC/DIV;

l your trigger settings should beAUTO for MODE, INT forSOURCE, and CH for INT

Turn your scope on with theprobe connected to the channel1 BNC connector and the probeadjustment jack. Use the foldoutfigure to remind yourself of thecontrol locations and follow thedirections in Exercise 5.

Figure 13.THE TRIGGER CIRCUIT AND ITS CON-TROLS are shown in the diagram above.Trigger source describes whether or notthe trigger signal is internal or external tothe scope. Coupling controls the con-nection of an external trigger to the trig-ger circuit. The level and slope controlsdetermine where the trigger point will beon the trigger signal. And the mode con-trol determines the operations of thetrigger circuit.

Exercise 5. TRIGGER CONTROLS

1. Move the trace to the rightwith the horizontal POSITIONcontrol until you can see thebeginning of the signal (you’llprobably have to increase theintensity to see the faster verticalpart of the waveform). Watch thesignal while you operate theSLOPE control. If you pick + , thesignal on the screen starts with arising edge; the other SLOPEcontrol position makes thescope trigger on a falling edge.2. Now move the LEVEL controlback and forth through all itstravel; you’ll see the leadingedge climb up and down thesignal. The scope remainstriggered because you areusing the AUTO setting.3. Turn the MODE switch toNORM. Now when you use theLEVEL control to move the trig-ger point, you’ll find placeswhere the scope is untriggered.This is an illustration of the es-sential difference between nor-mal and automatic triggering.

4. You can also see the differ-ence between the two triggeringmodes by using channel 2, evenwith that channel coupled toGND for ground. Change boththe vertical display mode andthe INT (2275:A&B INT)switches to CH 2. With NORMtriggering, there’s no signal;with AUTO, you’ll see thebaseline. Try it.5. Without a trigger signalapplied to the EXT INPUT BNCconnector, it’s impossible toshow you the use of this triggersource, but the trigger MODE,SLOPE, and LEVEL controls willall operate the same for eitherinternal or external triggers. Onedifference between internal andexternal sources, however, isthe sensitivity of the trigger cir-cuit. All external sources aremeasured in voltage (say 750millivolts) while the in ternalsources are rated in divisions. Inother words, for internal signals,the displayed amplitude makes

a difference. Now change theVERTICAL MODE and INTswitches back to CH 7, andswitch to the NORM mode. Usethe LEVEL control and noticehow much control range thereis. Now change the CH 7VOLTS/D/V switch to 0.7 V anduse the LEVEL control. There’smore control range now.6. The alternate-channel trigger-ing with vertical mode triggeringcan’t be demonstrated withouttwo unrelated signals on thechannels, but you’ll find ituseful the first time such an oc-casion comes up. You can takeanother look at the differencebetween the normal and autotrigger operating modes. Movethe LEVEL control slowly in theNORM mode until the scope isuntriggered. Now switch thetrigger operating mode to AU TOand note that the waveform isautomatically triggered.

16

CHAPTER 5. ALL ABOUT PROBES PART I

Connecting all the measure-ment test points you’ll need tothe inputs of your oscilloscope isbest done with a probe like theone illustrated in Figure 14.Though you could connect thescope and circuit-under-testwith just a wire, this simplest ofall possible connections wouldnot let you realize the fullcapacities of your scope. Theconnection would probably loadthe circuit and the wire wouldact as an antenna and pick upstray signals - 60 Hz power,CBers, radio and tv stations -and these would be displayedon the screen along with thesignal of interest.

Circuit LoadingUsing a probe instead of a barewire minimizes stray signals, butthere’s still an effect from puttinga probe in a circuit called circuitloading. Circuit loading modi-fies the environment of the sig-nals in the circuit you want tomeasure; it changes the signalsin the circuit-under-test, either alittle or lot, depending on howgreat the loading is.

Circuit loading is resistive,capacitive, and inductive. Forsignal frequencies under 5 kHz,the most important componentof loading is resistance. To avoidsignificant circuit loading here,all you need is a probe with aresistance at least two orders ofmagnitude greater than the cir-cuit impedance (100 Ma probesfor 1 Ma sources; 1 MSZ probesfor IO k0 sources, and so on).

When you are making mea-surements on a circuit that con-tains high frequency signals, in-ductance and capacitance be-come important. You can’t avoidadding capacitance when youmake connections, but you canavoid adding more capacitancethan necessary.

One way to do that is to use anattenuator probe; its designgreatly reduces loading. In-stead of loading the circuit withcapacitance from the probe tip

plus the cable plus the scope’sown input, the 10X attenuatorprobe introduces about tentimes less capacitance, as littleas IO-14 picofarads (pF). Thepenalty is the reduction in signalamplitude from the 1O:1attenuation.

These probes are adjustableto compensate for variations inoscilloscope input capacitanceand your scope has a referencesignal available at the frontpanel. Making this adjustment iscalledprobe compensation andyou did it as the first step inExercise 3 of Chapter 2.

Remember when you aremeasuring high frequencies,that the probe’s impedance (re-sistance and reactance)changes with frequency. Theprobe’s specification sheet ormanual will contain a chart likethat in Figure 15 that shows thischange. Another point to re-member when making high fre-quency measurements is to besure to securely ground yourprobe with as short a groundclip as possible. As a matter offact, in some very high fre-quency applications a specialsocket is provided in the circuitand the probe is plugged intothat.

Measurement SystemBandwidthThen there is one more probecharacteristic to consider:bandwidth. Like scopes, probeshave bandwidth limitations;each has a specified rangewithin which it does not at-tenuate the signal’s amplitudemore than -3 dB (0.707 of theoriginal value). But don’t as-sume that a 60 MHz probe and a60 MHz scope give you a 60MHz measurement capability.The combination will approxi-mately equal the square root ofthe sum of the squares of therise times (also see Chapter 10).

Figure 14.PROBES CONNECTTHE SCOPE AND THE CIRCUIT-UNDER-TEST. Tektronix probesconsist of a patented resistive cable and a grounded shield. Two P6120 probes andthe accessories pictured above are supplied with every 2200 Series scope. Theprobe is a high impedance, minimum loading 1O X passive probe. The accessoriesfor each probe (from left to right) are: a grabber tip for ICs and small diameter leads; aretractable hook tip; and IC tester tip cover; an insulating ground cover; markerbands; and (in the center) the ground lead.

For example, if both probe andscope have rise times of 5.83nanoseconds:

T r (system) = v Tr21scof3el + Tr2(probe)

T,=d34+34

That works out to 8.25nanoseconds, the equivalent toa bandwidth of 42.43 MHz be-cause:

B wlmegahertz) =350

T r (nanoseconds)

To get the full bandwidth fromyour scope, you need morebandwidth from the probe. Or

you use the particular probe de-signed for that instrument. Forexample, in the case of the 2200Series scopes and the P612010X Passive Probe, the probeand the scope have been de-signed to function together andyou have the full 60 MHz band-width at the probe tip..

17

ALL ABOUT PROBES CONT.

Probe Types PROBE TYPESGenerally you can divide probesby function, into voltage-sensing and current-sensingtypes. Then voltage probes canbe further divided into passiveand active types. One of theseshould meet your measurementrequirements.

1 X passive,voltage-sensing

10X/100X/1000Xpassive,voltage-sensing,attenuator

active,voltage-sensing,FET

current-sensing

high voltaae

CHARACTERISTICS

No signal reduction, which allows the maximum sensitivityat the probe tip; limited bandwidths: 4-34 MHz; high capacitance:32-l 12 pF; signal handling to 500 V

Attenuates signals; bandwidths to 300MHz; adjustable capacitance; signalhandling to 500 V (10X), 1.5 kV (100X),or 20 kV (1000X)

Switchable attenuation; capacitance as low as 1.5 pF; moreexpensive, less rugged than other types; limited dynamic range; butbandwidths to 900 MHz; minimum circuit loading

Measure currents from 1 mA to 1000 A; DC to 50 MHz; very low loading

Signal handling to 40 kV

Figure 15.PROBE IMPEDANCE IS RELATEDTO FREQUENCY as shown in the table above.The curves plot both resistance (R) and reactance (X) in ohms against frequency inmegahertz. The plot shown is for the Tektronix P6120 probe on a l-meter cable.

Picking A ProbeFor most applications, theprobes that were supplied withyour scope are the ones youshould use. These will usuallybe attenuator probes. Then, tomake sure that the probe canfaithfully reproduce the signalfor your scope, the compensa-tion of the probe should be ad-justable. If you’re not going touse the probes that came withyour scope, pick your probe

based on the voltage you intendto measure. For example, ifyou’re going to be looking at a50 volt signal and your largestvertical sensitivity is 5 volts, thatsignal will take up ten major divi-sions of the screen. This is asituation where you need at-tenuation; a 10X probe wouldreduce the amplitude of yoursignal to reasonable propor-tions.

Proper termination is impor-tant to avoid unwanted reflec-tions of the signal you want tomeasure within the cable.Probe/cable combinations de-signed to drive 1 megohm(1 MCI) inputs are engineered tosuppress these reflections. Butfor 50 fl scopes, 50 fl probesshould be used. The propertermination is also necessarywhen you use a coaxial cableinstead of a probe. If you use a50 a cable and a 1 MSZ scope,be sure you also use a 50 flterminator at the scope input.

The probe’s ruggedness, itsflexibility, and the length of thecable can also be important (butremember, the more cablelength, the more capacitance atthe probe tip). And check thespecifications to see if thebandwidth of the probe is suffi-cient, and make sure you havethe adapters and tips you’llneed. Most modern probes fea-ture interchangeable tips andadaptors for many applications.Retractable hook tips let you at-tach the probe to most circuitcomponents. Other adaptorsconnect probe leads to coaxialconnectors or slip over squarepins. Alligator clips for contact-ing large diameter test pointsare another possibility.

But for the reasons alreadymentioned (probe bandwidth,loading, termination), the bestway to ensure that your scopeand probe measurement sys-tem has the least effect on yourmeasurements is to use theprobe recommended for yourscope. And always make sureit’s compensated.

18

PART Il. MAKING MEASUREMENTS

The first five chapters describedhow to select the exact oscillo-scope functions you need tomake the measurements youwant. Now you can put whatyou’ve learned into practice withthis section of the primer.

It begins with a review ofwaveform shapes and charac-teristics in Chapter 6. Then the

discussions in Chapter 7 startwith safety because you shouldalways observe safety precau-tions when working on electricalequipment.

The first step in ensuring ac-curate measurements is makingsure your scope is set up prop-erly, and this subject is dis-cussed in Chapter 8.

Chapter 9 discusses mea-surement techniques, begin-ning with fundamental time andamplitude measurements andending with delayed sweepmeasurements.

The last chapter in the primerdescribes oscilloscope per-formance and how it affects yourmeasurements.

CHAPTER 6. WAVEFORMSThe definition of a wave is “adisturbance traveling through amedium” while the definition of awaveform is “a graphic repre-sentation of a wave.”

Like a wave, a waveform isdependent on two things:movement and time. The rippleon the surface of a pond existsas a movement of water in time.The waveform on your scope’sscreen is the movement of anelectron beam during time.

The changes in the waveformwith time form the waveshape,the most readily identifiablecharacteristic of a waveform.Figure 16 illustrates some com-mon waveshapes.

Figure 16.BASIC WAVESHAPES include sinewaves, and various non-sinusoidalwaves such as triangle waves, squarewaves, and sawtooth waves. A squarewave has equal amounts of time for itstwo states. Triangle and sawtooth wavesare usually the result of circuits de-signed to control voltage with respect totime, like the sweep of an oscilloscopeand some television circuits. In thesewaveforms, one (or both) transitionsfrom state to state are made with a

SINE WAVE

steady variation at a constant rate, aramp. (Changes from one state toanother on all waveforms except sinewaves are called transitions.) The lasttwo drawings represent aperiodic,single-shot waveforms. The first is apulse; all pulses are marked by a rise, afinite duration, and a decay. The secondone is a step, which is actually a singletransition.

-fRIAIWLE WAVE

PUISE STEP

19

MAKING MEASUREMENT CONT.

Waveshapes tell you a greatdeal about the signal. Anytimeyou see a change in the verticaldimension of a signal, you knowthat this amplitude change rep-resents a change in voltage.Anytime there’s a flat horizontalline, there was no change forthat length of time. Straightdiagonal lines mean a linearchange, equal rise (or fall) ofvoltage for equal amounts oftime. Sharp angles on awaveform mean a suddenchange. But waveshapes aloneare not the whole story. Whenyou want to completely describea waveform, you’ll want to findthe parameters of that particularwaveform. Depending on thesignal, these parameters mightbe amplitude, period, fre-quency, width, rise time, orphase. You can review thesesignal parameters with Figures17 through 22.

Figure 17.AMPLITUDE IS A CHARACTERISTIC OFALL WAVEFORMS. It is the amount ofdisplacement from equilibrium at a par-ticular point in time. Note that without amodifier, the word means the maximumchange from a reference without regardto the direction of the change. In the firsttwo drawings above (sine wave andsquare wave), the amplitude is the sameeven though the sine wave is larger frompeak to peak. In the third drawing, analternating current waveform is shownwith peak (or maximum) amplitude andpeak-to-peak amplitude parametersannotated. In oscilloscope measure-ments, amplitude usually means peak-to-peak amplitude.

SINE WA= STWTIME-

SQUARE WAVE

ERIOQI - l

Figure 18.PERIOD IS THE TIME REQUIRED FOR ONE CYCLE OF A SIGNAL if the signalrepeats itself. Period is a parameter whether the signal is symmetrically shaped likethe sine and square waves above, or whether it has a more complex and asymmetri-cal shape like the rectangular wave and damped sine wave. Period is alwaysexpressed in units of time. Naturally, one-time signals like the step or uncorrelatedsignals (without a time relation) like noise have no period.

2 0

PART II

Figure 19.IF A SIGNAL IS PERIODIC, IT HAS A FREQUENCY. Frequency is the number of timesa signal repeats itself in a second; frequency is measured in Hertz: 1 Hz = 1 cycle persecond; 1 kHz (kilohertz) = 1000 cycles/second; and 1 MHz (megahertz) =1 ,OOO,OOO cycles/second. Period and frequency are reciprocal: l/period = fre-quency, and l/frequency = period. For example, a 7 Hz signal has a period of 0.143seconds: 1/7 Hz = 0.143 s, and 1/0.143 s = 7 Hz.

Figure 20.THE PARAMETERS OF A PULSE can be important in a number of different applica-tions. Digital circuitry, X-ray equipment, and data communications are examples.Pulse specifications include transition times measured on the leading edge of apositive-going transition; this is the rise time. Fall time is the transition time on anegative-going trailing edge. Pulse width is measured at the 50% points andamplitude from 0 to 100%. Any displacement from 0 volts for the base of the pulse isthe baseline offset.

Figure 21.DUTY CYCLE, DUTY FACTOR, ANDREPETITION RATE are parameters of allrectangular waves. They are particularlyimportant in digital circuitry. Duty cycleis the ratio of pulse width to signal periodexpressed as a percentage. For squarewaves, it’s always 50% as you can see;for the pulse wave in the second draw-ing, it’s 30%. Duty factor is the samething as duty cycle except it is ex-pressed as a decimal, not a percentage.A repetition rate describes how often apulse train occurs and is used instead offrequency to describe waveforms likethat in the second drawing.

Figure 22.PHASE is best explained with a sinewave. Remember that this waveform isbased on the sine of all the angles from 0through 360. The result is a plot thatchanges from 0 to 00,l at 900,O again at1800, -1 at 270”, and finally 0 again at360”. Consequently, it is useful to refer tothe phase angle (or simply phase, whenthere is no ambiquity) of a sine wavewhen you want to describe how much ofthe period has elapsed. Another use ofphase is found when you want to de-scribe a relationship between two sig-nals. Picture two clocks with their sec-ond hands sweeping the dial every 60seconds. If the second hands touch thetwelve at the same time, the clocks are inphase; if they don’t, then they’re out ofphase. To express how far out of phasethey are, you use phase shift in degrees.To illustrate, the waveform labeledCURRENT in the drawing above is saidto be 90” out of phase with the voltagewaveform. Other ways of reporting thesame information are “the currentwaveform has a 90 degree phase anglewith respect to the voltage waveform” or“the current waveform lags the voltagewaveform by 9OO.” Note that there is al-ways a reference to another waveform;in this case, between the voltage andcurrent waveforms of an inductor.

21

CHAPTER 7. SAFETY

Before you make any oscillo-scope measurement, rememberthat you must be careful whenyou work with electrical equip-ment. Always observe all safetyprecautions described in theoperators or service manual forthe equipment you’re workingon.

Some general rules aboutservicing electrical equipmentare worth repeating here. Don’t

service electrical devices alone.Know the symbols for danger-ous circuits and observe thesafety instructions for theequipment you’re working on.Don’t operate an electrical de-vice in an explosive atmos-phere. Always ground the scopeto the circuit, and ground bothyour scope and the circuit-

under-test. Remember that ifyou lose the ground, all ac-cessible conductive parts - in-cluding knobs that appear to beinsulated - can give you ashock. To avoid personal injury,don’t touch exposed connec-tions and components in thecircuit-under-test when thepower is on. And remember toconsult the service manual forthe equipment you’re workingon.

Then there are few rules aboutthe scope itself: To avoid ashock, plug the power cord ofthe scope into a properly-wiredreceptacle before connectingyour probes; only use the powercord for your scope, and don’tuse one that isn’t in good condi-tion (cracked, broken, missingground pin, etc.). Use the rightfuse to avoid fire hazards. Don’tremove covers and panels onyour scope.

CHAPTER 8. GETTlNG STARTEDAccurate oscilloscope mea-surements require that youmake sure your system is prop-erly setup each time you beginto use your scope.

Compensating the ProbeMost measurements you makewith an oscilloscope require anattenuator probe, which is anyprobe that reduces voltage. Themost common are 10X (“timesten”) passive probes which re-duce the amplitude of the signaland the circuit loading by 10:1.

But before you make anymeasurement with an attenuatorprobe, you should make sure it’scompensated. Figure 23 illus-trates what can happen to thewaveforms you’ll see when theprobe is not properly compen-sated.

Note that you should com-pensate your probe as it will beused when you make the mea-surement. Compensate it withthe accessory tip you’ll be usingand don’t compensate theprobe in one vertical channeland then use it on another.

Checking the ControlsThe most common mistake inmaking oscilloscope measure-ments is forgetting to compen-sate the probe. The secondmost frequent source of inac-curacies is forgetting to checkthe controls to make sure they’rewhere you think they are. Hereare some things to check onyour Tektronix 2200 Seriesscope (arranged according tothe functional blocks of yourscope):

l Check all the vertical systemcontrols: variable controls (CH1 and CH 2 variable VOLTS/DIV) should be in their cali-brated detent positions; makesure CH 2 isn’t inverted (unlessyou want it to be); check thevertical mode switches tomake sure the signal from theproper channel(s) will be dis-played; check the two verticalsystem VOLTS/DIV switches tosee if their settings are right(and don’t forget to use theVOLTS/DIV readout thatmatches the probe, either IX or10X); check the input couplinglevers too.

l Check the horizontal systemcontrol settings: magnificationis off (push in the red VARswitch in the middle of theSEC/DIV switch); variableSEC/DIV is in its calibrated de-tent position. Make sure thehorizontal mode switch iswhere you need it: NO DLYwhen you’re not making de-layed sweep measurements,INTENS for making measure-ments with an intensified zone,or DLY’D if you want a delayedsweep (A, ALT or B on a 2215).

l Then check your trigger sys-tem controls to make sure yourscope will pick the right slopeon the trigger signal, that theright coupling is selected, andthat the correct operatingmode will be used. Also makesure that the trigger variableholdoff control is at its mini-mum position.

Handling a ProbeBefore you probe a circuit, youshould make sure you have theright probe tips and adaptors forthe circuits you will be workingon. (Tips available for the Tek-tronix P6120 10X probes wereshown in Figure 14, Chapter 5.)

Then make sure that theground in the circuit-under-testis the same as the scope ground- don’t just assume it is. Thescope ground will always beearth ground as long as you’reusing the proper power cordand plug. Check the circuitground by touching the probetip to the point you think isground before you make a hardground by attaching the groundstrap of your probe.

If you’re going to be probing alot of different points in the samecircuit and measuring frequen-cies less than 5 MHz, you canground that circuit to your scopeonce instead of each time youmove the probe. Connect thecircuit ground to the jackmarked GND on the front panel.

22

GETTING STARTED CONT. PART II

Figure 23.IMPROPERLY COMPENSATED PROBES can distort the waveforms you see on thescreen of your scope. In the photographs the probe adjustment signal and a 1 MHzsquare wave are shown as they will appear with proper and improper compensa-tions. Notice the amplitude and ringing changes on the square wave with thedifferences in compensation.

23

CHAPTER 9. MEASUREMENT TECHNIQUES

Rather than attempt to describehow to make every possiblemeasurement, this chapter de-scribes common measurementtechniques you can use in manyapplications.

The Foundations: Amplitudeand Time MeasurementsThe two most basic measure-ments you can make areamplitude and time; almostevery other measurement you’llmake is based on one of thesetwo fundamental techniques.

Since the oscilloscope is avoltage-measuring device, volt-age is shown as amplitude onyour scope screen. Of course,voltage, current, resistance, andpower are related:

current = -!!GF-resistance

resistance = voltagecurrent

power = current x voltage

Amplitude measurements arebest made with a signal thatcovers most of the screen verti-cally. Use Exercise 6 to practicemaking amplitude measure-ments.

Time measurements are alsomore accurate when the signalcovers a large area of thescreen. Continue with the set-upyou had for the amplitude mea-surement, but now use Exercise7 to make a period measure-ment.

Exercise 6. AMPLITUDE MEASUREMENTS

1. . Connect your probe to thechanne l 7 BNC connector and tothe probe adjustment jack. At-tach the probe ground strap tothe collar of the channel 2 BNC.Make sure your probe is com-pensated and that all the vari-able controls are set in their de-tent positions.2. The trigger MODE switchshould be set to NORM for nor-mal triggering. The HORIZON-TAL MODE should be NO DLY (Aon the 2275). Make sure thechannel 7 coupling switch is setto AC and that the triggerSOURCE switch is on internaland the /N T switch on CH 7. Setthe VERTICAL MODE switch toCH 7 as well.3. Use the trigger LEVEL controlto obtain a stable trace andmove the volts /division switchuntil the probe adjust squarewave is about five divisionshigh. Now turn the seconds/division switch until two cyclesof the waveform are on your

screen. (The settings should be0.7 V on the VOLTS/D/V and 0.2ms on the SEC/D/ V switches.)4. Now use the CH 7 verticalPOSITION control to move thesquare wave so that its top is onthe second horizontal gra ticuleline from the top edge of thescreen. Use the horizontal posi-tion control to move the signal sothat the bottom of one cycle in-tersects the center verticalgra ticule line.

5. Now you can count major andminor divisions down the centervertical graticule line and multi-ply by the VOLTSIDI V setting tomake the measurement. Forexample, 5.0 divisions times 0.7volts equals 0.5 volts. (If thevoltage of the probe adjustmentsquare wave in your scope isdifferent from this example,that ’s because this signal is nota critical part of your scope andtight tolerances and exact cali-bration are not required.)

Exercise 7. TIME MEASUREMENTS

Time measurements are bestmade with the center horizontalgraticule line. Use the instru-ment settings from Exercise 6and center the square wave ver-tically with the vertical POSI-TION control. Then line up onerising edge of the square wavewith the gra ticule line that ’s sec-ond from the lefhdan d side of thescreen with the HORIZONTALposition control. Make sure thenext rising edge intersects thecenter horizontal graticule.Count major and minor divisionsacross the center horizontalgraticule line from left to right asshown in the photo above. Mul-tiply by the SEC/D/ V setting; forexample, 5.7 divisions times 0.2

milliseconds equals 7.74 milli- this example, remember thatseconds. (If the period of the this signal is not a critical part ofprobe adjustment square wave the calibration of your scope.)in your scope is different from

24

PART II

Frequency and Other DerivedMeasurementsThe voltage and time measure-ments you just made are twoexamples of direct measure-ments. Once you’ve made a di-rect measurement, there are de-rived measurements you cancalculate. Frequency is oneexample; it’s derived fromperiod measurements. Whileperiod is the length of time re-quired to complete one cycle ofa periodic waveform, frequencyis the number of cycles that takeplace in a second. The mea-surement unit is a hertz (1cycle/second) and it’s the recip-rocal of the period. So a periodof 0.00114 second (or 1 .14 mil-liseconds) means a frequencyof 877 Hz.

More examples of derivedmeasurements are the alternat-ing current measurements illus-trated by Figure 24.

Pulse MeasurementsPulse measurements are impor-tant when you work with digitalequipment and data communi-cations devices. Some of thesignal parameters of a pulsewere shown in Figure 20, butthat was an illustration of anideal pulse, not one that exists inthe real world. The most impor-tant parameters of a real pulseare shown in Figure 25.

Use Exercise 8 to make de-rived measurements with theprobe adjustment square wave.

Figure 24.DERIVED MEASUREMENTS are the re-sult of calculations made after directmeasurements. For example, alternat-ing current measurements require anamplitude measurement first. Theeasiest place to start is with a peak-to-peak amplitude measurement of thevoltage - in this case, 330 volts be-cause peak-to-peak measurements ig-nore positive and negative signs. Thepeak voltage is one-half that (when thereis no DC offset), and is also called amaximum value; it’s 165 V in this case.Theaverage value is the total area underthe voltage curves divided by the periodin radians; in the case of a sine wave, theaverage value is 0 because the positiveand negative values are equal. The RMS(root mean square) voltage for this sinewave - which represents the line volt-age in the United States- is equal tothe maximum value divided by thesquare root of 2: 165 + 1.414 = 117 volts.You get from peak-to-peak to RMS volt-age with: peak-to-peak + 2 x the squareroot of 2.

l+--fEpIoP -I

Figure 25.REAL PULSE MEASUREMENTS include a few more parameters than those for anideal pulse. In the diagram above, several are shown. Preshooting is a change ofamplitude in the opposite direction that precedes the pulse. Overshooting androunding are changes that occur after the initial transition. Ringing is a set ofamplitude changes - usually a damped sinusoid -that follows overshooting. Allare expressed as percentages of amplitude. Settling time expresses how long ittakes the pulse to reach it maximum amplitude. Droop is a decrease in the maximumamplitude with time. And nonlinearity is any variation from a straight line drawnthrough the 10 and 90% points of a transition.

Exercise 8. DERIVED MEASUREMENTS

With the period measurementyou just made in Exercise 7, cal-culate the frequency of theprobe adjustment square wave.For example, if the period is 7millisecond, then the frequencyis the reciprocal, 7 IO.007 or 7000Hz. Other derived measure-ments you can make are dutycycle, duty factor, and repetitionrate. Duty cycle is the ratio ofpulse width to signal period ex-pressed as a percentage: 0.5ms t 7 ms, or 50%. But youknew that because for squarewaves, it’s always 50%. Dutyfactor is 0.5. And the repetitionrate (describing how often apulse train occurs) is 7 /second

in this case because repetitionrate and frequency are equal forsquare waves. Your probe ad-justment tsignal might differslightly from this example; cal-culate the derived measure-ments for it. You can also calcu-late the peak, peak-to-peak,and average values of the probeadjustment square wave in yourscope, Don’t forget that youneed both the alternating anddirect components of the signalto make these measurements,so be sure to use direct coupling(DC) on the vertical channelyou’re using.

MEASUREMENT TECHNIQUES CONT.

Use the directions in Exercise9 to make a pulse measurementon the probe adjustment squarewave.

Exercise 9.PULSE WIDTHMEASUREMENTS

To measure the pulse width ofthe probe adjustment squarewave quickly and easily, set yourscope to trigger on and displaychannel 7. Your probe shouldstill be connected to the channel7 BNC connector and the probeadjustment jack from the previ-ous exercises. Use 0.7 ms /division and the no delay hori-zontal mode (A sweep if you’reusing a 2275). Use AUTO trig-gering on the positive slope andadjust the trigger LEVEL controlto get as much of the leadingedge as possible on yourscreen. Switch the coupling onchannel 7 to ground and centerthe baseline on the center hori-zontal graticule. Now use ACcoupling because that will cen-ter the signal on the screen andyou make pulse width mea-surements at the 50 % point ofthe waveform. Use your horizon-tal POSITION control to line upthe 50 % point with the first majorgraticule from the left side of thescreen. Now you can count divi-sions and subdivisions acrossthe center horizontal and multi-ply by the SEC/D/V switch set-ting to find the pulse width.

Phase MeasurementsYou know that a waveform hasphase, the amount of time thathas passed since the cycle be-gan, measured in degrees.There is also a phase relation-ship between two or morewaveforms: the phase shift (ifany). There are two ways tomeasure the phase shift be-tween two waveforms. One is byputting one waveform on eachchannel of a dual-channelscope and viewing them directlyin the chop or alternate verticalmode; trigger on either channel.Adjust the trigger LEVEL controlfor a stable display and mea-sure the period of the wave-forms. Then increase the sweepspeed so that you have a dis-play something like the seconddrawing back in Figure 22. Thenmeasure the horizontal distancebetween the same points on thetwo waveforms. The phase shiftis the difference in time dividedby the period and multiplied by360 to give you degrees.

Displaying the two waveformsand measuring when one startswith respect to another is possi-ble with any dual trace scope,but that isn’t the only way tomake a phase measurement.Look at the front panel and you’llsee that the vertical channelBNC connectors are labeled Xand Y. The last position on theSEC/DlV switch is XY, and whenyou use it, the scope’s time baseis bypassed. The channel 1input signal is still the horizontalaxis of the scope’s display, butnow the signal on channel 2 be-comes the vertical axis. In theX-Y mode, you can input onesinusoidal on each channel andyour screen will display a Lissa-jous pattern. (They are namedfor Jules Antoine Lissajous, aFrench physicist; say “LEE-za-shu”). The shape of the patternwill indicate the phase differ-ence between the two signal.Some examples of Lissajouspatterns are shown in Figure 26.

Note that general purposeoscilloscope Lissajous patternphase measurements are usu-ally limited by the frequency re-sponse of the horizontal ampli-fier (typically designed with farless bandwidth than verticalchannels). Specialized X-Yscopes or monitors will have al-most identical vertical and hori-zontal systems.

X-Y MeasurementsFinding the phase shift of twosinusoidal signals with a Lissa-jous pattern is one example ofan X-Y measurement. The X-Ycapability can be used for othermeasurements as well. The Lis-sajous patterns can also beused to determine the fre-quency of an unknown signalwhen you have a known signalon the other channel. This is avery accurate frequency mea-

surement as long as your knownsignal is accurate and both sig-nals are sine waves. The pat-terns you can see are illustratedin Figure 26, where the effects ofboth frequency and phase dif-ferences are shown.

Component checking in ser-vice or production situations isanother X-Y application; it re-quires only a simple transistorchecker like that shown in Fig-ure 27

There are many other applica-tions for X-Y measurements intelevision servicing, in engineanalysis, and in 2-way radio ser-vicing, for examples. In fact, anytime you have physical phe-nomena that are interdependentand not time-dependent, X-Ymeasurements are the answer.Aerodynamic lift and drag,motor speed and torque, or

+ oooo/\oovooo”zo30f45 90 135” 700’

3 v\MDoooNooov\0” 15O 30° 60” TO” lZO”

Figure 26.FREQUENCY MEASUREMENTS WITH LISSAJOUS PATTERNS require a known sinewave on one channel. If there is no phase shift, the ratio between the known andunknown signals will correspond to the ratio of horizontal and vertical lobes of thepattern. When the frequencies are the same, only the shifts in phase will affect thepattern. In the drawings above, both phase and frequency differences are shown.

26

PART II

Figure 27.X-Y COMPONENT CHECKING requires the transistor checker shown above. With itconnected to your scope and the scope in the X-Y mode, patterns like thoseillustrated indicate the component’s condition. The waveforms shown are foundwhen the components are not in a circuit; in-circuit component patterns will differbecause of resistors and capacitors associated with the component.

pressure and volume of liquids Differential Measurementsand gasses are more examples. The ADD vertical mode and theWith the proper transducer, you channel 2 INVERT button of yourcan use your scope to make any 2200 Series scope let you makeof these measurements. differential measurements.

Often differential measurementslet you eliminate undesirablecomponents from a signal thatyou’re trying to measure. If youhave a signal that’s very similarto the unnecessary noise, theset up is simple. Put the signalwith the spurious information onchannel 1. Connect the signalthat is like unwanted compo-nents to channel 2. Set bothinput coupling switches to DC(use AC if the DC components ofthe signal are too large), andselect the alternate verticalmode by moving the VERTICALMODE switches to BOTH andALT

Now set your volts/divisionswitches so that the two signalsare about equal in amplitude.Then you can move the right-hand VERTICAL MODE switchto ADD and press the INVERTbutton so that the commonmode signals have oppositepolarities.

If you use the channel 2VOLTS/DIV switch and VAR con-trol for maximum cancellation ofthe common signal, the signalthat remains on-screen will onlycontain the desired part of thechannel 1 input signal. The twocommon mode signals havecancelled out leaving only thedifference between the two.

Figure 28.DIFFERENTIAL MEASUREMENTS allow you to remove unwanted information from asignal anytime you have another signal that closely resembles the unwanted com-ponents. For example, the first photo shows a 1 kHz square contaminated by a 60 Hzsine wave. Once the common-mode component (the sine wave) is input to channel 2and that channel is inverted, the signals can be added with the ADD vertical mode.The result is shown in the second photo.

Using the Z AxisRemember from Part I that the

CRT in your scope has threeaxes of information: X is the hori-zontal component of the graph,Y is the vertical, and Z is thebrightness or darkness of theelectron beam. The 2200 Seriesscopes all have an externalZ-axis input BNC connector onthe back of the instrument. Thisinput lets you change thebrightness (modulate the inten-sity) of the signal on the screenwith an external signal. The

Z-axis input will accept a signalof up to 30 V through a usablefrequency range of DC to 5 MHz.Positive voltages decrease thebrightness and negative volt-ages increase it; 5 volts willcause a noticeable change.

The Z-axis input is an advan-tage to users that have their in-struments set up for a longseries of tests. One example isthe testing of high fidelityequipment illustrated byFigure 29.

27


c SCOPE

Figure 29.USING THE Z-AXIS can provide additional information on the scope screen. In theset-up drawn above, a function generator sweeps through the frequencies of interestduring the product testing-20 to 20,OOO Hz, in this case. Then an adjustable notchfilter is used to generate a marker, at 15 kHz, for instance, and this signal is applied tothe Z-axis input to brighten the trace. This allows the tester to evaluate the product’sperformance with a glance.

Using TV TriggeringThe composite video waveformconsists of two fields, each ofwhich contains 262 lines. Manyscopes offer television trigger-ing to simplify looking at videosignals. Usually, however, thescope will only trigger on fieldsat some sweep speeds andlines at others. The 2200 Seriesscopes allow you to trigger oneither lines or fields at anysweep speed.

To look at tv fields with a 2200Series scope, use the TV FIELD

28

mode. This mode allows thescope to trigger at the field rateof the composite video signal oneither field one or field two.Since the trigger system cannotrecognize the difference be-tween field one and field two, itwill trigger alternately on the twofields and the display will beconfusing if you look at one lineat a time.

To prevent this, you add moreholdoff time, and there are twoways to do that. You can use thevariable holdoff control, or you

can simply switch the verticaloperating mode to display bothchannels. That makes the totalholdoff time for one channelgreater than one field period.Then just position the unusedvertical channel off-screen toavoid confusion.

It is also important to selectthe trigger slope that corre-sponds to the edge of thewaveform where the syncpulses are located. Picking anegative slope for pulses at thebottom of the waveform allowsyou to see as many sync pulsesas possible.

When you want to observe theTV line portion of the compositevideo signal, use the NORMtrigger mode and trigger on thehorizontal synchronizationpulses for a stable display. It isusually best to select the blank-ing level of the sync waveformso that the vertical field rate willnot cause double triggering.

Delayed SweepMeasurementsDelayed sweep is a techniquethat adds a precise amount oftime between the trigger pointand the beginning of a scopesweep. Often delayed sweep isused as a convenient way tomake a measurement (the risetime measurement in Exercise10 is a good example). To makea rise time measurement withoutdelayed sweep, you must trig-ger on the edge occurring be-fore the desired transition, Withdelayed sweep, you maychoose to trigger anywherealong the displayed waveformand use the delay time control tostart the sweep exactly whereyou want.

Sometimes, however, de-layed sweep is the only way tomake a measurement. Supposethat the part of the waveform youwant to measure is so far fromthe only available trigger pointthat it will not show on thescreen The problem can besolved with delayed sweep:trigger where you have to. and

delay out to where you want thesweep to start.

But the delayed sweep fea-ture you’ll probably use the mostoften is the intensified sweep; itlets you use the delayed sweepas a positionable magnifier. Youtrigger normally and then usethe scope’s intensified horizon-tal mode. Now the signal on thescreen will show a brighter zoneafter the delay time. Run thedelay time (and the intensifiedzone) out to the part of the signalthat interests you. Then switch tothe delayed mode and increasethe sweep speed to magnify theselected waveform portion sothat you can examine it in detail.

Since the 2200 Series has twotypes of delayed sweep, readthe paragraphs and use the de-layed sweep measurementexercise below that applies toyour scope: “Single Time BaseScopes” and Exercise 10 for de-layed sweep measurementswith single time base scopeslike the Tektronix 2213; or “DualTime Base Scopes” and Exer-cise 11 for delayed sweep ondual time base scopes like the2215.

Single Time Base ScopesVery few single time basescopes offer delayed sweepmeasurements. Those that domay have measurementcapabilities similar to those ofthe Tektronix 2213 which hasthree possible horizontal opera-ting modes annotated on thefront panel as NO DLY, INTENS,and DLY’D.

When you set the HORIZON-TAL MODE switch to NO DLY (nodelay), only the normal sweepfunctions.

When you choose INTENS (in-tensified sweep), your scopewill display the normal sweepand the trace will also be inten-sified after a delay time. Theamount of delay is determinedby both the DELAY TIME switch(you can use 0.5 ps, 10 ps, or0.2 ms) and the DELAY TIMEMULTIPLIER control. The multi-

PART II

plier lets you pick from 1 to 20times the switch setting.

The third position, DLY ’D (de-layed), makes the sweep startafter the delay time you ’ve cho-sen. After selecting this positionyou can move the SEC/DIV to afaster sweep speed andexamine the waveform ingreater detail.

This list of horizontal modesshould begin to give ideas ofhow useful these delayedsweep features are. Start bymaking the rise time measure-ment described below. (Notethat when making rise timemeasurements, you must takethe rise time of the measuringinstrument into account. Be sureto read Chapter IO.)

Dual Time Base ScopesDelayed sweep is normallyfound on dual time base scopeslike the 2215 with two totallyseparate horizontal sweepgenerators. In dual time baseinstruments, one sweep istriggered in the normal fashionand the start of the secondsweep is delayed. To keep thesetwo sweeps distinct when de-scribing them, the delayingsweep is called the A sweep; thedelayed sweep is called the Bsweep. The length of time be-tween the start of the A sweepand the start of the B sweep iscalled the delay time.

Dual time base scopes offeryou all the measurementcapabilities of single time baseinstruments, plus:l convenient comparisons of

signals at two different sweepspeeds

l jitter-free triggering of delayedsweeps

l and timing measurement ac-curacy of 1.5%.Most of this increase in mea-

surement performance is avail-able because you can sepa-rately control the two sweepspeeds and use them in threehorizontal operating modes.These modes - in a 2215 - are

Exercise 10.2213 DELAYED SWEEP MEASUREMENTS

1. Connect your probe to thechannel 7 BNC connector andthe probe adjustmentjack, hookthe ground strap onto the collarof the channel2 BNC, and makesure the probe is compensated.2. Use these control settings:CH 7 VOLTS/D/V on 0.2 usingthe 10X probe VOLTS/DIV read-out; CH 7 input coupling on AC;VERTICAL MODE is CH 7;TRIGGER MODE is AUTO;TRIGGER SLOPE is negative(-); trigger SOURCE is INT (forinternal) and INT trigger switchis either CH 7 or VERT MODE;HORIZONTAL MODE is NO DLY;SEC/DIV is 0.5 ms. Check all thevariable controls to make surethey’re in their calibrated detentpositions.3. Set the input coupling to G NDand center the trace. Switchback to AC and set the triggerLEVEL control for a stable dis-play. The waveform should looklike the first photo above.

A sweep only, B sweep only, or Aintensified by B as well as B de-layed. The HORIZONTALMODE switch controls the oper-ating mode and two SEC/DIVswitches - concentricallymounted on a 2215 -controlthe sweep speeds. See Figure30.

When you use the ALT (for al-ternate horizontal mode) posi-tion the HORIZONTAL MODEswitch, the scope will displaythe A sweep intensified by the B

4. Because a rise time mea-surement is best made at fastersweep speeds, turn the SEC/DIV control to 2 w. Use the trig-ger LEVEL control to try to get allof the positive transition on thescreen. You can’t; you lose yourtrigger when you get off theslope of the signal.5. Turn back to 0.5 msldiv andswitch to the intensified displaywith the HORIZONTAL MODEswitch. Switch the DELAY TIMEto 0.2 ms and use the DELAYTIME MULTIPLIER to move theintensified zone on thewaveform to a point before thefirst complete positive-goingtransition of the square wave.The intensified zone now showsyou where the delayed sweepwill start, like the second photo.

6. Switch the horizontal mode toDLY’D and the SEC/DIV switchto 5 p. Now you can use thehorizontal POSITION andDELAY TIME MULTIPLIER con-trols to get a single transition onthe screen.

sweep and the B sweep de-layed. As you set faster sweepswith the B SEC/DlV switch, you’llsee the intensified zone on the Atrace get smaller and the Bsweep expanded by the newspeed setting. As you move theB DELAY TIME POSITION dialand change where the B sweepstarts, you’ll see the intensifiedzone move across the A traceand see the B waveformchange.

7. Change to 0.7 Vldiv and lineup the signal with the 0 and700% dotted lines of thegraticule. (If you have a signalthat doesn’t fit between the 0and 700% lines of the graticule,you have to count major andminor divisions and estimate therise time while ignoring the firstand last 70% of the transition.)

8. Use the horizontal POSITIONcontrol to move the waveformuntil it crosses a verticalgraticule line at the 70% mark-ing. Adjust the FOCUS controlfor a sharp waveform and makeyour rise time measurementfrom that vertical line to wherethe step crosses the 90% line.Now you can make a rise timemeasurement on a waveformlike that in the third photograph.For example, for 7 major divisionand 4 minor divisions: 7.8 timesthe SEC/DIV setting of 5 wis9*.

This sounds more compli-cated in words than it is in prac-tice. As you use the scope inExercise 11, you’ll find that theprocedure is very easy. You willalways see exactly where the Bsweep starts. And you can usethe size of the intensified zone tojudge which B sweep speed youneed to make the measurementyou want.

29


Measurements at Two SweepSpeedsLooking at a signal with two dif-ferent sweep speeds makescomplicated timing measure-ments easy. The A sweep givesyou a large slice of time on thesignal to examine. The inten-sified zone will show you wherethe B sweep is positioned. Andthe faster B sweep speedsmagnify the smaller portions ofthe signal in great detail. You’llfind this capability useful inmany measurement applica-tions; see Figure 31 for twoillustrations.

Because you can use thescope to show A and B sweepsfrom both channel 1 and chan-nel 2, you can display fourtraces. To prevent overlappingtraces, most dual time basescopes offer an additional posi-tion control. On the 2215, it’slabeled ALT SWP SEP for alter-nate sweep separation. With itand the two vertical channelPOSITION controls, you canplace all four traces on-screenwithout confusion.

Separate B TriggerJitter can prevent an accuratemeasurement anytime you wantto look at a signal that isn’t per-fectly periodic. But with two timebases and delayed sweep, youcan solve the problem with theseparate trigger available forthe B sweep. You trigger the Asweep normally and move theintensified zone out to the por-tion of the waveform you want tomeasure. Then you set thescope up for a triggered Bsweep, rather than letting the Bsweep simply run after the delaytime.

On a 2215, the B TRIGGERLEVEL control does double duty.In its full clockwise position, itselects the run-after-delaymode. At any other position, itfunctions as a trigger level con-trol for the B trigger. The BTRIGGER SLOPE control letsyou pick positive or negativetransitions for the B trigger.

With these two controls youcan trigger a stable B sweepeven when the A sweep hasjitter.

Increased TimingMeasurement AccuracyBesides examining signals attwo different sweep speeds andseeing a jitter-free B sweep, youget increased timing measure-ment accuracy with a dual timebase scope.

Note that the B DELAY TIMEPOSITION dial is a measuringindicator as well as a positioningdevice. The numbers in the win-dow at the top of the dial arecalibrated to the major divisionsof the scope screen. The num-bers around the circumferencedivide the major division intohundreds.

To make timing measure-ments accurate to 1.5% with theB DELAY TIME POSITION dial:l use the B runs-after-delay

mode.l place the intensified zone (or

use the B sweep waveform)where the timing measurementbegins, and note the B DELAYTIME POSITION dial setting

l dial back to where the mea-surement ends and note thereading there

l subtract the first reading fromthe second and multiply by theA sweep SEC/DlV setting.You’ll find an example of this

accurate - and easy - timingmeasurement in Exercise 11.

Figure 30.THE DELAYED SWEEP CONTROLS of the dual time base 2215 are shown on thephotograph above. They include: HORIZONTAL MODE (under the horizontal POSI-TION control); B TRIGGER SLOPE and LEVEL; ALT SWP SEP (alternate sweepseparation, between the two vertical POSITION controls - not shown), and aconcentric A and B SEC/DlV control. The B DELAY TIME POSITION dial is at thebottom of the column of horizontal system controls.

Figure 31.ALTERNATE DELAYED SWEEP MEASUREMENTS are fast and accurate. One use,examining timing in a digital circuit, is demonstrated in the firs t photograph. Supposeyou need to check the width of one pulse in a pulse train like the one shown. To makesure which pulse you are measuring, you want to look at a large portion of a signal.But to measure the one pulse accurately, you need a faster sweep speed. Looking atboth the big picture and a small enlarged portion of the signal is easy with alternatedelayed sweep. Another example is shown in the second photo. Here one field of acomposite video signal is shown in the first waveform. The intensified portion of thatfield is the lines magnified by the faster B sweep. With a dual time base scope, youcan walk through the field with the B DELAY TIME POSITION dial and look at each lineindividually.

30

PART II

Exercise 11.2215 DELAYED SWEEP MEASUREMENTS

Rise Time Measurement

1. Connect your probe to thechannel 7 BNC connector andthe probe adjustmentjack, hookthe ground strap onto the collarof the channel2 BNC, and makesure the probe is compensated.2. Use these control settings:CH 7 VOLTS/DIV on 0.2 (re-member to use the 10X probereadout); CH 7 input coupling onAC; VERTICAL MODE is CH 7; ATRIGGER MODE is NORM; ATRIGGER SLOPE is negative(-); A SOURCE is INT and theA&B INT trigger switch is eitherCH 7 or VERT MODE; HORI-ZONTAL MODE is A; A and BSEC/DIV is 0.2 ms. Check thevariable controls to make surethey’re in their calibrated detentpositions.3. Set the A TRIGGER LEVELcontrol for a stable display andposition the waveform in the tophalf of the screen. Switch to theALT (for alternate A and Bsweeps) display with the HORI-ZONTAL MODE switch. Use thechannel 7 POSITION and ALTSWP SEP (alternate sweep sep-aration) controls to position thetwo sweeps so that they don’toverlap.4. Use the B DELAY TIME POSI-TION dial to move the beginningof the intensified zone a pointbefore the first complete posi-tive transition. Your screenshould look like the first photoabove.

5. Pull out on the SEC/DIV knoband rotate it clockwise tochange the B sweep speed to 2,us /division. This will make theintensified zone smaller; move itto the first rising edge of thewaveform as in the secondphotograph.6. Switch the horizontal mode toB, the channel 7 vertical sensitiv-ity to 0.7 volts/division, and thesweep speed to 7 ,usldivision.Use the horizontal and verticalPOSITION controls and the BDELAY TIME POSITION controlto line up the waveform with the0 and 700% dotted lines of thegraticule. (If you have a signalthat doesn’t fit between the 0and 700% lines of the graticule,you have to count major andminor divisions and estimate therise time while ignoring the firstand last 10%.)

7. Position the waveform so thatit crosses a vertical graticule lineat the 70% marking. Adjust theFOCUS control for a sharp

waveform and count major andminor divisions across thescreen to where the stepcrosses the 90% line. If there are4 major and 8 minor divisions, 4and 8/10 times the SEC/DIV set-ting of 7 p is 4.8 p. The thirdphoto shows how the screenshould look now. (Note: Any jitteryou see in the B sweep is fromthe probe adjustment circuit, notthe time base.)8. One last word on rise timemeasurements: the accuracy ofthe measurement you make de-pends on both the signal you’reexamining and the performanceof your scope. In Chapter 70,you’ll find a description of howthe scope’s own rise time affectsyour measurement results.

Pulse Width Measurement

1. Use these control settings:CH 7 VOLTS/D/V on 0.7; CH 7input coupling on AC; VERTI-CAL MODE is CH 7; A TRIGGERMODE is NORM; A TRIGGERSLOPE is negative (-); A TRIG-

GER SOURCE is INT (for inter-nal) and INT trigger switch iseither CH 7 or VERT MODE;HORIZONTAL MODE is A; ASEC/DIV is 0.2 ms while BSEC/DIV is 0.05 w. Check thevariable controls.2. Center the first completepulse of the waveform horizon-tally. Switch to the A LT displaywith the HORIZONTAL MODEswitch and move the Bwaveform to the bottom of thescreen with the ALT SWP SEPcontrol.3. Center A sweep waveformvertically. Turn down the inten-sity so that it’s easier to see thesmall intensified zone.4. Move the intensified zone tothe 50% point of the rising edgeof the waveform with the DELAYTIME POSITION controlas in thefirst photo above. Note the delaytime reading (the number in thewindow first, for example: 3.7).Move the intensified zone to the50% point of the trailing edge asin the second photo and notethe reading.5. The time measurement, apulse width in this case, is equalto the second dial readingminus the first times the A sweepspeed: 5.77 - 3.73 x 0.2 ms =0.528 ms. In other words, the BDELAY TIME POSITION dial in-dicates screen divisions for you,7 complete turn for every majordivision.

31

INDEX

AA sweep 29A/B SWP SEP 8AC coupling 6Alternate horizontal operating

mode 10Alternate sweep separation

control 8Amplitude 20Amplitude measurements 24Attenuation 6

BB delay time position control 11B sweep 29BNC 8Bandwidth and rise time 33Bandwidth specifications 33Beam finder control 4Blanking 14

CCapacitance 17Cathode ray tube (CRT) 2Channel 2 inversion control 7Circuit loading 17Compensating the probe 9Compensation box 9Coupling 6

DDC coupling 6Deflection voltages 6Delay time 29Delay time control 11Delay time multiplier (DTM)

control 10Delayed sweep 28Delayed sweep measurements

28Delaying sweep 29Derived measurements 25Differential measurements 27Display system 4Divisions 4Dual time base scopes 29Duty cycle 21Duty factor 21

EElectron beam 4Exercises, 24

Amplitude measurement 24Controlling vertical

sensitivity 9Compensating the probe 9Delayed sweep 29Scope initialization 3Signal coupling 9Time measurement 24Using the display controls 5Using the horizontal

controls 12Using the trigger controls 16Using the vertical controls 9Vertical operating mode 9

External triaaerina 6

FFrequency measurements 25Focus control 4

GGND input coupling 6Graticule 4

HHoldoff 14Horizontal magnification

control 11Horizontal operating mode

control 10Horizontal position control 10Horizontal system 10

Initialization 3Input coupling control 6Internal triggering 14Intensified sweep 28Intensity control 4

LLine triggering 15Lissajous figures 26

MMagnification 11Major divisions 4Measurement system band-

width 17Measurement techniques,

Amplitude 24Differential 27Delayed sweep 28Derived 25Fall time 25Frequency 25Period 24Phase 26Pulse 25Pulse width 26Rise time 29Time 24video 28X-Y 26

Minor divisions 4

0Oscilloscope performance 32

34

PART II

PParallax errors 4Period 24Phase 21Picking a probe 18Phase measurements 26Phosphor 4Position controls,

horizontal 10vertical 6

Probes,accessories 17attenuator 18adjustment jack 4bandwidth 17compensation 17current 18handling 22loading 17passive 18

Pulse measurements 25

RRamp 10Repetition rate 21Retrace 10Rise time and bandwidth 33Rise times, scope and mea-

surement 32

SSafety 22Sawtooth waves 19Scale factors 6SEC/DIV control 10Screen 4Sine waves 19Single time base scopes 28Square waves 19Square wave and high fre-

quency response 32Steps 19Subdivisions 4Sweep generator 10Sweep speeds 10

TTelevision triggering 28Termination 18Time base 10Time measurements 24Trace rotation control 5Transducers 2Transitions 19Triangle waves 19Trigger,

automatic mode (AUTO) 15coupling control 16external 14holdoff control 14internal 14line 15level control 12normal mode (NORM) 15operating modes control 15point 13slope control 12source control 14system 12TV FIELD mode 15

UUnblanking 14

VVariable SEC/DlV control 11Variable trigger holdoff

control 14Variable VOLTS/DIV control 7Vertical operating mode

control 7Vertical operating modes, 7

ADD 8ALT (alternate) 7BOTH 7CHOP 7CH1 7CH27

Vertical mode triggering 15Vertical position control 6Vertical sensitivity control 6Vertical system 6Vertical system coupling 6VOLTS/DIV control 6

WWaveforms,

Pulse 19Sawtooth 19Sine 19Square 19Step 19Triangle 19

XX axis 5X-Y measurements 26

YY axis 5

ZZ axis 5

35

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