ef lab 01 - dmm and resistors

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Electrical Fundamentals – EECE1470

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Lab Exercise 1 – DMM, Breadboards, Resistors, and DC Voltage

Objectives

To gain experience working with the lab equipment.

To classify resistors in accordance with standard color code.

To compare estimated to actual resistance and discuss tolerance.

To measure DC voltage.

Equipment

A 10K Ω and a 1K Ω resistor

Digital Multimeter (DMM)

Breadboard (BB)

Two meter leads one red and one black.

Two banana leads c/w clips one red and one black.

Breadboard

The breadboard (prototype board) is used to quickly build and test a circuit. Components and wires are

inserted into the holes in the board to make the required electrical connections.

In Figure 1, you can see wires used to help create the path. The

components are inserted into the holes in the board. Some components

allow electrical current to run in only one direction, while for others,

the direction does not matter.

Note: the large component in the middle is an assembly of several

components.

Figure 1

Figure 2 shows how the breadboard holes are connected.

Note:

The 2 parallel side rows and many middle rows run at 90° to each

other, and are not connected to each other.

The middle rows are separated by gap that runs down the middle.

Some boards also separate the side rows into 2 sections, top and

bottom.

Figure 2

The top wire brings current from one side row to the middle row. All three

devices have one terminal on this power row. (Assume that power is supplied tothe side row somewhere else.)

The current flows through the devices and returns along the bottom middle

row, through the wire and back along the other side row.

Figure 3





Resistors

Resistors can be grouped into two broad categories, fixed and variable. Variable resistors are often

referred to as potentiometers (pots) or rheostats. In this lab students test several fixed resistors. The

physical size of the fixed resistor relates to its power handling capability (watt rating - for later

discussion). Resistance readings are taken with power off and at least one end of the resistor disconnected from a circuit. For this lab no power is required and the resistors are not connected.

Resistors have a colour code that indicates the resistor value, and the unit of measurement is the ohm (Ω).

On page 4 of to the lab is a chart with the colour codes. If you do not have a chart, you may use a phrase

like the following to remember the colour values.

Black Beetles Running On Your Garden Bring Very Good WeatherBad Beer Rots Our Young Guts, But Vodka Goes Well

The phrase will help you remember the weight of the colour bands.

Black Brown Red Orange Yellow Green Blue Violet Gray White

Measuring Resistance Ω (ohms)

Never perform resistance measurements on live circuits.To measure resistance

1. Attach the red test lead to the terminal marked for ohms (Ω).

2. Attach the black test lead to the terminal marked COM.

3. Set the meter scale to measure 20k or lower in the Ω section of the scale. Note: when only the figure

“1” is displayed, it indicates an over range situation, and a higher range must be selected.

4. Connect the test leads across the resistance (ie. resistor). Do not hold the resistor in your hand while

taking a measurement. Your body may change the reading you receive.

Procedure After the introduction and/or additional instructions are received from the instructor:

1. Using the colour code chart, find the resistor values listed in the following table.

2. Insert the resistors into the BB as per above.3. Verify the values using the DMM.

4. Calculate the difference between the nominal value and the actual. Calculate the difference as a % of

the nominal value.

Enter all measurements and calculations in the working section of the lab (pages 1 to 4). For the lab

report, hand in the submission sheets (pages 5 and 6) only. Each student must hand in their own lab

report. Each report must have a title page.

Table 1

Nominal

Value

1st Band

colour

2nd Band

colour

X

colour

Tolerance

Value

Actual

Value

Diff. %

diff.

1K Ω

10K Ω





Measuring Voltage in a DC circuit.

V

When a multi-meter is connected to measure DC voltage, NEVER EVER turn the selector switch to

a current or ohm range. You may damage the meter.

1. Make sure the red test lead is attached to the terminal marked for volts (V).

2. Attach the black test lead to the terminal marked COM.

3. If you are unsure of the voltage, set the meter to the highest rating. For this lab, set the meter scale to

measure 20v in the V section of the scale. When only the figure “1” is displayed, it indicates an over

range situation, and a higher range must be selected.

4. Voltage is measured across any component through which current flows, so connect the positive (red)

terminal of the meter to the point which is electrically closest to the positive side of the component

your are measuring across. Connect the negative (black) terminal to the other side of the component.

Procedure

1. Build the circuit shown on the schematic below on your breadboard. For R1 use the 1K resistor. For

R2 use the 10k resistor.

2. Set the power supply voltage to 10 volts.

3. Measure and record in table 2, the voltage at V1, V2 and V3.

Table 2

Schematic

Demonstrate how you took your measurements to your instructor. Be sure the instructor initials the

submission sheet.

Questions

1. Use Ohms Law to calculate the total current through the circuit. Use the measured voltage and

actual resistor values in your calculation. (Hint: You will need to find the total resistance first.)

2. Calculate what the voltage should be at V1, V2 and V3 based on your answer from 1.

Measured Voltage

V1(R 1=1K)

V2(R 2=10K)

V3(R T)

R1

PS 10VDC

R2

V V1

V V2

+

+

-

-

V V3

+

-





Lab Exercise 1 – DMM, Breadboards, Resistors and Ohms Law

Submission Sheet

All labs require a title page with lab title, course name, instructor name, date and your name. See the

scratch drive (k:\) for an example. Neatness counts. Lab reports are due at the START of your nextscheduled lab period. Late labs will not be accepted.

Table 1

Nominal

Value

1st Band

colour

2nd Band

colour

X

colour

Tolerance

value

Actual

resistance

Diff. %

Diff.

1K Ω

10K Ω

Schematic

Instructor Initials:_______________

1. Use Ohms Law to calculate the total current through the circuit. Use the measured voltage and

actual resistor values in your calculation. (Hint: You will need to find the total resistance first.)

2. Calculate what the voltage should be at V1, V2 and V3 based on your answer from 1.

Measured Voltage

V1(R 1=1K)

V2(R 2=10K)

V3(R T)

R1

PS 10VDC

R2

V V1

V V2

+

+

-

-

V V3

+

-





Marking Scheme

/2 Completed/demonstrated the lab and initialed by the lab instructor.

/1 Title page

/1 Neatness

/1 Table 1 correct

/1 Measured voltages complete

/1 Question 1 calculations

/1 Question 1 correct answer

/1 Question 2 example calculation

/1 Question 2 correct answer

/10 Total

ef lab 01 - dmm and resistors

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