qbw scale - adam equipment usa...@adam equipment company 2004 3 n scale range = 1.5 kilograms...

Adam Equipment

QBW Scale

SERVICE MANUAL

ADAM EQUIPMENT CO. LTD. p.n. 6064, Rev. A, June 2005

@Adam Equipment Company 2004

CONTENTS

INTRODUCTION .................................................................................................................2 SPECIFICATIONS...............................................................................................................2 SCALE RANGES AND RESOLUTIONS..............................................................................2 TROUBLE SHOOTING GUIDE ...........................................................................................4 DISPLAY AND KEYS...........................................................................................................5 POWER ...............................................................................................................................5 ZERO / TARE ......................................................................................................................6 WEIGHING UNITS SELECTION .........................................................................................7 CALIBRATION.....................................................................................................................7 USER SETUP PARAMETERS ............................................................................................8

FUNCTION OF THE KEYS..............................................................................................8 BUZZER ON/OFF ............................................................................................................9 AUTO SWITCH-OFF TIME ..............................................................................................9 ENABLED UNITS...........................................................................................................10

VIEWING ADC COUNTS...................................................................................................10 LOADING DEFAULTS.......................................................................................................10 ERRORS ...........................................................................................................................11 QBW HARDWARE OVERVIEW ........................................................................................12 QBW ASSEMBLY..............................................................................................................16 LOAD CELL ASSEMBLY...................................................................................................19

@Adam Equipment Company 2004 2

INTRODUCTION

• The QBW series of scales are simple, easy to use scales with an internal rechargeable battery.

• The weighing process is fast and accurate, making it suitable for general purpose weighing applications.

• There are 5 models in this series with capacities ranging from 1.5 kilograms to 30 kilograms.

• All have stainless steel weighing platforms on an ABS plastic base assembly. • Keypads are sealed, with colour coded membrane switches. • The displays are large, easy to read liquid crystal type displays (LCD). • The LCD normally shows the weight and the previously-selected units of the weight

(Grams, Kilograms, Ounces, Pounds or Pounds & Ounces).

SPECIFICATIONS Operating temperature 0ºC TO 40ºC

32ºF TO 104ºF

Battery Internal Rechargeable Battery (approx. 150 hours Operation)

Power Supply Adapter 9 VAC, 500mA

Applications General Purpose Weighing Scale

Stabilisation Time 2 seconds typical

Calibration Manual External

Display 4 and 1/2 Digits LCD Display

Balance Housing ABS Plastic, Stainless Steel Platform

Pan Size 225 X 275 mm (8.9” X 10.8”)

Dimensions ( W X D X H) 315 x 355 x 110 mm (12.4”X14”X4.3”)

Gross weight Approx. 4.0 Kg (8.8 lb.)

SCALE RANGES AND RESOLUTIONS 5 different ranges and resolutions are available for the scale, depending on the weighing range of the load cell fitted and its associated software. The ranges and resolutions for each capacity in all the available units are shown in the following tables:


N

SCALE RANGE = 1.5 kilograms

SELECTED UNITS

FULL SCALE DISPLAY RESOLUTIO DISPLAY

Grams 1500.0 g 1500,0 g 0.5 g 0,5g Kilograms 1.500 kg 1,500 kg 0.001 kg 0,001 kg Ounces 52.90 oz 52,90 oz 0.02 oz 0,02 oz Pounds 3.306 lb 3,306 lb 0.002 lb 0,002 lb Pounds & Ounces 1 lb15.9 oz* 1_15,9 lb-oz 0.1 oz _ 0,1 lb-oz

SCALE RANGE = 3 kilograms

SELECTED UNITS

FULL SCALE DISPLAY RESOLUTION

DISPLAY

Grams 3000 g 3000 g 1 g 1 g Kilograms 3.000 kg 3,000 kg 0.001 kg 0,001 kg Ounces 105.80 oz 105,80 oz 0.05 oz 0,05 oz Pounds 6.615 lb 6,615 lb 0.005 lb 0,005 lb Pounds & Ounces 6 lb 10 oz 6_10 lb-oz 1 oz 0_ 1 lb-oz


SELECTED UNITS


DISPLAY

Grams 6000 g 6000 g 2 g 2g Kilograms 6.000 kg 6,000 kg 0.002 kg 0,002 kg Ounces 211.6 oz 211,6 oz 0.1 oz 0,1 oz Pounds 13.23 lb 13,23 lb 0.01 lb 0,01 lb Pounds & Ounces 13 lb 4 oz 13_ 4 lb-oz 1 oz 0_ 1 lb-oz


SELECTED UNITS


DISPLAY

Grams 15000 g 15000 g 5 g 5 g Kilograms 15.000 kg 15,000 kg 0.005 kg 0,005 kg Ounces 529.0 oz 529,0 oz 0.2 oz 0,2 oz Pounds 33.06 lb 33,06 lb 0.02 lb 0,02 lb Pounds & Ounces 19 lb 15 oz* 19_15 lb-oz 1 oz 0_ 1 lb-oz


SELECTED UNITS


DISPLAY

Grams 19999 g* 19999 g 10 g 10 g Kilograms 30.00 kg 30,00 kg 0.01 kg 0,01 kg Ounces 1058.0 oz 1058,0 oz 0.5 oz 0,5 oz Pounds 66.15 lb 66,15 lb 0.05 lb 0,05 lb Pounds & Ounces 19 lb 15 oz* 19_15 lb-oz 1 oz 0_ 1 lb-oz

*NOTE: Ranges marked with an asterisk are limited by the range of displayable numbers, not by the maximum capacity of the scale, and will show an “E Or” message when the result is over range, rather than an “E OL” message when the scale is overloaded.


TROUBLE SHOOTING GUIDE

SYMPTOM POSSIBLE CAUSE SUGGESTIONS Blank display when the [On] key is pressed without the charger being connected.

Battery discharged. Battery disconnected.

Plug in mains power supply /charger. Check battery connections.

Blank display when [On] is pressed with charger connected.

Internal power cable is disconnected. Keypad cable is disconnected.

Reconnect cable from power supply board to the main board. Reconnect cable from keypad to the main board.

Display shows “E Hi” at power up.

Load present on weight pan.

Switch off instrument. Remove load from weight pan. Switch on again.

Display shows “E Lo” at power up.

Weighing pan not fitted. Load cell disconnected.

Switch off instrument. Fit plastic and metal weight pan. Switch on again. Check connections between load cell and the main board.

Weighing readings are incorrect.

Scale requires re-calibration.

Recalibrate using external reference mass.

Weighing readings are unstable.

Draught or vibration. Ensure scale is placed on a firm, vibration-free surface away from sources of draught.

Display shows “E OL” during weighing.

Weighing pan is overloaded.

Remove weight from pan.

Display shows “E Or” during weighing.

Weight value is too large to be displayed in currently-selected units.

Remove weight from pan or select alternative units.

Charge LED does not illuminate when charger plugged in.

No mains supply to the charger.

Check the wall socket.

Charge LED shows green but scale does not function without charger connected.

Battery faulty or disconnected. Internal fuse on power supply board blown.

Check battery connections. If connections OK, replace battery. Replace fuse with one of the same rating.

Charge LED remains red after several hours of charging.

Battery faulty. Replace battery.

DISPLAY AND KEYS

POWER The scale is turned on by pressing the [On] key. There should be no load on the scale when power is applied. When the scale first powers up, the display will show the software revision number in the form “rX.XX”. After about 2 seconds the display will then show the rated scale capacity. This will be in the form “C XX kg”, where XX is the capacity in kilograms if the last selected units were Grams or Kilograms, or “C XX lb”, where XX is the capacity in pounds if the last selected units were Pounds, Ounces or Pounds & Ounces. After a further 2 seconds all the display segments will turn on for approximately 2 seconds. The scale is then zeroed and displays a zero reading, accompanied by the last selected units. If the reading from the scale indicates that a load is in place on the scale at power-up, an error message “E Hi” will flash on the display for about 5 seconds. If the reading from the scale indicates that the weighing pan is not in place on the scale at power-up, an error message “E Lo” will flash on the display for about 5 seconds. The scale will then operate, but will not have established a new no-load value. In order to achieve this, the scale should be powered down, the load removed or the weighing pan fitted, and the scale powered up again. The scale is turned off by pressing the [Off] key or by the timed automatic power-off function (if enabled). A voltage detector is also included, which is used to indicate a low battery condition by displaying the battery symbol. If the scale is not then attached to a charger or manually switched off, the electronics will subsequently shut down the scale, even if the automatic power-off is disabled.


ZERO / TARE A zero or tare operation may be performed at any time by pressing and then releasing the [Zero/Tare] key. The display will show “- - - -” until the key is released, followed by the message “tArE” during tare value measurement, then the displayed weight value will be set to zero. If the tare reading is within a small range of the initial no-load value established at switch on, the zero indicator will be displayed and the scale will still have the maximum capacity available for weighing before an overload condition is displayed. If however the tare reading is greater than this small range, indicating that a weight is present, the scale will tare. The weight value will still be displayed as zero, but will show the tare indicator instead of the zero indicator and the additional capacity before an overload condition is displayed will be reduced by the amount of weight on the scale when it was last tared. If the scale is unable to obtain a stable weight value during the taring process after a number of retries, it will display an error message “E St”, then abort the tare attempt and return to weighing. Whenever the scale is subsequently displaying a zero value, either the zero or the tare indicator will be displayed.

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Lo

Whenever a weight is put othen when the reading hasbe on at all times during no

@Adam Equipment Company

Tare table Zero

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n to the scale the zero, tare and stable symbols will all turn off,

stabilised, the stable symbol will turn on. The units symbol will rmal weighing.

2004 6


WEIGHING UNITS SELECTION The desired weighing units may be selected by pressing the [Units] key (display shows “- - - -”) and then releasing it. The display will select each of the available units of weight in turn, indicating the currently-selected units and the current weight value in the new units. The units available for selection are set in the user set-up function as described below. NOTE: If there is sufficient weight on the scale to cause the display to go out of range when an alternative unit is selected, an “E Or” error message will be displayed. If this occurs, the load should be removed, or the [Units] key should be pressed and then released to select the next alternative unit.

CALIBRATION It is only possible to perform a calibration of the scale using a single value of standard mass which is equal, or near to, the maximum capacity of the scale. If metric units (i.e. Grams or Kilograms) are selected, the value of the calibration mass required is the maximum capacity of the scale in Kilograms. If imperial units (i.e. Pounds, Ounces or Pounds & Ounces) are selected, the value of the calibration mass required is in Pounds as shown in the following table:

Maximum Scale Capacity (kg)

Calibration Mass (lb)

1.5 3 3 5 6 10 15 30 30 60

The software includes checks to prevent the calibration from being performed if there is no weight or a grossly incorrect weight on the scale, or it is overloaded. Procedure:

• Press and hold the [Cal] key. The display shows “- - - -”. After 3 seconds the display will change to “C 0”. Release the key. If the [Cal] key is released within 3 seconds, the calibration request will be ignored and the scale will return to normal weighing.

• Ensure that there is no weight on the balance, and then press the [Cal] key again. The display will show “tArE”. Release the key.

• If the no-load calibration value is acceptable, the display will then show “C XX uu” where XX is the value of calibration mass required, and uu is the units (lb or kg) for the calibration mass, e.g. “C 6 kg” for a 6 kilogram mass, or “C 10 lb” for a 10 pound mass.


• Place the correct calibration mass on the scale.

• Press the [Cal] key again. The display will show “CAL ”. Release the key. The display will continue to show “CAL ” until calibration is complete and then return to normal weighing, when it should display the correct calibration weight value in the currently-selected units.

NOTE: If the no-load or full-load reading is too low, an “E Lo” error will be displayed.

If the no-load or full-load reading is too high, an “E Hi” error will be displayed. If the no-load or full-load reading is unstable, an “E St” error will be displayed. If any of these conditions occur, or if [Cal] is not pressed within 10 seconds of the “C 0” message being displayed, the calibration procedure will be aborted and the scale will return to normal weighing using the previous tare and calibration values.

USER SETUP PARAMETERS

FUNCTION OF THE KEYS To enter the user-parameter setup menu, the [Zero/Tare] key should be held pressed, and while the display is showing “- - - -” the [Units] key should be pressed. The first setup option will then be shown. Release both the keys. If [Zero/Tare] is released without the [Units] key being pressed, the display will change to “tArE”, a normal tare operation will be performed, and the setup menu will not be entered. When in the setup menu, the functions of the keys are as follows: Press [Zero/Tare] to select alternatives within any parameter. Press the [Cal] key (display shows “- - - -”) then release the key to save any changes to the current parameter, exit the setup menu, and return to normal weighing mode. Press the [Units] key to save any changes to the current parameter and move to the next setup parameter.

BUZZER ON/OFF

• The first option is to enable or disable the buzzer. The default state for this parameter is buzzer on.

• The display will show “bu X”, where X = 0 for buzzer off, X = 1 for buzzer on. • Press the [Zero/Tare] key to change the enabled state of the buzzer.

• Press the [Cal] key to save any change of buzzer state and return to normal

weighing.

• Press the [Units] key to save any change of buzzer state and move to the next setup parameter, which is to set the automatic switch-off time.

• If the buzzer is enabled, it will sound to acknowledge a valid key press or when an error condition is displayed.

AUTO SWITCH-OFF TIME

• The default value for this parameter is “OFF 0” (auto switch-off disabled).

• The display will show “OFF x”, where x = 0 to 9, representing the number of minutes of inactivity, i.e. if no key is pressed for the specified auto switch-off time displayed in minutes, the scale will automatically switch off. A value of 0 will disable the auto switch-off, while a value of 9 will cause the scale to switch off approximately 9 minutes after the last key was pressed.

• Press the [Zero/Tare] key to change the auto switch-off time, with an automatic roll-over from 9 to 0.

• Press the [Cal] key to save any change of auto switch-off time and return to normal

weighing.

• Press the [Units] key to save any change of auto switch-off time and move to the next setup parameter, which is to set the enabled units.


ENABLED UNITS The default setting for the enabled units is any of the available units i.e. Grams, Kilograms, Ounces, Pounds or Pounds & Ounces. NOTE: The currently-active unit cannot be disabled, hence to disable the current unit

an alternative unit must first be selected during normal weighing.

• The display will show the first non-active unit, together with “On” or “OFF” to indicate its currently-enabled state.

• Press the [Zero/Tare] key to change the enabled state of the currently-displayed unit.

• Press the [Units] key to save any change to the enabled state of the currently-

displayed unit and display the next non-active unit, together with its currently-enabled state.

• Press the [Cal] key to save any change of unit-enable state and return to normal

weighing.

VIEWING ADC COUNTS The ADC counts value may be viewed by holding the [Cal] and [Units] keys pressed simultaneously at the end of the power-on display test. The raw ADC counts as a number from 0 to 30,000 will be displayed, with 15,000 subtracted to give a displayed range of -15,000 to +15,000 counts. This mode can be exited at any time by pressing the [Cal] key, at which point the scale will return to normal weighing mode.

LOADING DEFAULTS This function can only be performed by holding the [Cal], [Units] and [Zero/Tare] keys pressed simultaneously at the end of the power-on display test, and should only be carried out by qualified technicians. Factory defaults will be loaded for the stored setup, zero and calibration values, then the raw ADC counts will be displayed as described above.



This mode can be exited at any time by pressing the [Cal] key, at which point, since the zero and calibration values have been defaulted, the scale will automatically enter a calibration routine as described above. A calibration procedure must then be carried out to ensure reading accuracy. It is therefore vital that a standard calibration mass is available for this purpose. A successful calibration at this point will return the scale to normal weighing mode, but any errors will be unrecoverable, and the scale must be switched off and back on again to allow the calibration to be completed. Normal weighing will not be possible until a successful calibration has been performed after loading the default values.

ERRORS During operation the software will attempt to ensure that the results obtained are sensible. Potential error messages and their causes are detailed in the following table:

At power-up

E Lo A/D counts more than 10% of scale capacity below default no-load value.

E Hi A/D counts more than 10% of scale capacity above default no-load value.

Taring

E St Taring could not be performed because the readings were not stable.

No-load Calibration

E Lo A/D counts more than 10% of scale capacity below default no-load value.

E Hi A/D counts more than 10% of scale capacity above default no-load value.

E St No-load value could not be determined because the readings were not stable.

Full-load Calibration

E Lo A/D counts more than 10% of scale capacity below default full-load value.

E Hi A/D counts more than 10% of scale capacity above default full-load value.

E St Full-load value could not be determined because the readings were not stable.

Weighing

E OL Weight is more than 0.03% (9d) above maximum range.

E Or Result exceeds range of display.


QBW HARDWARE OVERVIEW

Power Supply PCB This board converts the AC input from the mains adaptor to DC and provides a current-regulated supply to the internal 6 volt battery for charging purposes, as well as to the main ADC board. Two LED drive lines are also incorporated to provide battery charging indication. The incoming AC supply is rectified by the full-wave bridge rectifier BR1 to provide a raw DC supply, which is smoothed by C2 and filtered by C3. This raw DC is then used to supply a 14-pin DIL LM723 voltage regulator, which provides a voltage and current regulated supply via the NPN series pass transistor Q2. The values of resistors R1, R4 & R5 are chosen to give an output voltage of about 8 volts at the emitter of Q2. In order to maintain this voltage, the voltage on the Vcc pin of the regulator must be a minimum of about 11 volts. This means that the minimum input voltage from the mains adaptor must be at least 9 volts AC or 12 volts DC. The regulated voltage is then supplied to the battery and the ADC board via the 1.5 ohm high-wattage resistor R3. When the current drawn through R3 exceeds about 500mA, the voltage drop across it reaches about 0.7 volts, at which point the regulator begins to reduce the output voltage, thus limiting the output current. The mains adaptor therefore needs to be capable of supplying a continuous current of at least 500mA. The voltage drop across R3, and hence the voltage supplied to the ADC board and the battery will depend upon the amount of current being drawn from supply, which in turn will depend upon the charge state of the battery. With a fully-charged battery, this voltage will be about 7 volts, reducing as the charge current increases. If the output voltage on the Zener diode ZD1 exceeds 6.8 volts, it will conduct, supplying base current to Q1, which will turn on, turning Q3 on and Q4 off and supplying current via R12 to the ‘GN’ pin on PL2, which will illuminate the green ‘Battery OK’ LED on the ADC board. If the output voltage on the Zener diode ZD1 falls below 6.8 volts due to the regulator entering a current-limit state, it will cease to conduct, turning off Q1 and Q3 and turning on Q4, supplying current via R13 to the ‘RD’ pin on PL2, which will illuminate the red ‘Battery Low’ LED on the ADC board. The ADC board supply is provided by PL2 pins 1 (positive) & 2 (negative), while the battery is connected to PL1 pins 1 (positive) & 2 (negative), and protected by the fuse FS1.


Analogue to Digital Converter PCB This board consists of four main sections:

1. Power supply regulation and monitoring. 2. Dual-slope analogue to digital converter. 3. Microcontroller and associated digital components. 4. LCD display and driver.

1. Power supply regulation and monitoring The power for the board is provided in the form of a single DC supply (nominally 7 volts) via CONN1 pins #1 (positive) and #2 (negative) from the power supply board. This voltage is applied to the input of an LM2931 low-dropout 5 volt regulator via a series pass transistor Q2, which allows the board to be powered up or down under software control. When the [On] button is pressed, Q2 is turned on via R4, the microcontroller is powered up, and its output on pin #1 is immediately set high by the control program, turning on Q1 and holding the power on after the [On] button has been released. When the [Off] button is pressed, or the controller sets its pin #1 low, Q1 is turned off, turning off Q2 and disconnecting the power until the [On] button is pressed again. The output of the 5 volt regulator supplies the rest of the circuitry via separate digital and analogue tracks, which are commoned together at one point only, via inductor L1. The 0 volt returns are also tracked separately for the digital and analogue components and commoned together at one point only, via inductor L2. Since the minimum voltage difference required across the LM2931 to maintain regulation is about 0.3 volts, the DC input voltage to the board must be a minimum of about 5.1 volts to maintain the required supply to the ICs. If this voltage falls below about 5.25 volts, the output of the comparator formed by one of the operational amplifiers in the LM324 (U5d) will switch high. This output is monitored by an input on pin #17 of the controller, which will turn on the ‘Low battery’ indicator on the LCD when this occurs. A tri-colour common-cathode red / green LED is also mounted on the ADC board, with its common cathode connected to ground, its green anode connected to CONN1 pin #3, and its red anode connected to CONN1 pin #4. This LED is driven by two outputs from the power supply board, but is located on the ADC board to allow it to be viewed through a hole in the case next to the display. 2. Dual-slope analogue to digital converter The load cell used for weight measurement is a strain gauge, which is connected to the ADC board via the connector CONN3. Its excitation is provided by the analogue 5 volt supply and analogue ground through pins #1 (E+) and #4 (E-) via the two inductors L3 and L6. Since this excitation voltage is about 5 volts, and the output of the load cells used is 2 millivolts per volt, the output will vary from zero at no load to about 10 millivolts at full load.


This output voltage is connected via pins #2 (S-) and #3 (S+) of CONN3, and inductors L4 and L5, to the differential inputs of an OP-07 operational amplifier (U6). The cable from the strain gauge is screened for noise suppression, the screen being connected to analogue ground via CONN3 pin #5. Further noise suppression is provided by the filtering capacitors C19 to C22, which are commoned to a mid-rail (2.5 volt) reference point, and resistors R37 and R38. The input voltage from the load cell can be biased more positive by connecting resistor R39 from the inverting input of the amplifier to the analogue 5 volt supply via solder bridge SB2, or more negative by connecting resistor R40 from the non-inverting input of the amplifier to analogue ground via solder bridge SB3. These solder bridges are used to configure the desired offset for the different magnitudes of strain gauge used in the variants of the QBW scale. For the 1.5 and 3 kilogram scales, SB3 should be bridged and SB2 should be left open. For the 6, 15 and 30 kilogram scales, both SB2 and SB3 should be left open. Two different gains can also be configured for this amplifier by the use of solder bridge SB1, which connects R32 in parallel with the fixed gain resistor R34. This is used to configure one of two gains for the different magnitudes of strain gauge used in the variants of the QBW scale. For the 1.5 kilogram scale, SB1 should be left open. For the 3, 6, 15 and 30 kilogram scales, SB1 should be bridged. The output from this amplifier is fed into the inverting input of a low pass filter formed by the operational amplifier U5a, which has its non-inverting input set to a reference voltage of about 2.5 volts, then via resistors R25 and R24 into the inverting input of an integrator formed by the operational amplifier U5b, which has its non-inverting input set to a reference voltage of about 3 volts. The integrating capacitor C10 will therefore be charged to an amplified and filtered voltage proportional to the output of the load cell. This voltage is then applied to the non-inverting input of a comparator formed by U5c, the inverting input of which is set at a reference voltage of 1.25 volts. The output of this comparator can be read by the controller via an input on pin #8. The PNP transistor Q4 is controlled by the output on pin #20 of the controller. Setting this output low turns the transistor on, allowing the integrating capacitor to charge up towards 5 volts via R24. After the transistor has been turned on, the time taken for the inverted integrator output voltage level to fall to the point at which the comparator output switches low again depends on the voltage originally present on the integrator. Thus by switching off Q4 for a fixed period of time, then turning it on and measuring the time taken for the comparator to return low, a number can be obtained which is proportional to the load-cell output. This number is read by the controller as an A to D counts value.


3. Microcontroller and associated digital components The microcontroller used is a Philips 87LPC764 in a 20-pin DIL plastic package. This interfaces with the other areas of the circuit as follows: Using a serial I2C-compatible bus, the controller interfaces to a Philips PCF8576 display driver chip (see below) and also to a 24C01 serial EEPROM containing 1 Megabit (256 Kbytes) of non-volatile memory. The serial clock (SCL) and serial data (SDA) lines are pulled up to the digital 5 volt supply by resistors R14 and R15. The port pins #1 and #17 are configured as output and input respectively, and are used to interface the controller to the power control and monitoring circuitry as described above. The port pins #20 and #8 are configured as output and input respectively, and are used to interface the controller to the analogue to digital converter circuitry as described above. Port pins #13, #14 & #15 are configured as inputs and used to detect key presses from the [Tare], [Units] and [Cal] switches. These inputs are normally pulled high by resistors R11, R12 & R13 and are then pulled low when a switch is pressed, which connects the input to ground. The [On] and [Off] switches are connected directly into the power supply control circuitry, and are not interfaced via the controller. Port pin #2 is configured as an output, which is used to drive a buzzer via transistor Q3. Since the reset state for all outputs on the controller is high, a PNP transistor connected to the digital 5 volt supply is used, so that an output high state turns the buzzer off and setting the output low turns the buzzer on. Port pins #3 and #4 are connected via linkable headers to ground, and can be read by the software for configuration or security purposes. If no link is fitted to the header, the inputs are pulled high by internal pull-up resistors. Pins #6 and #7 are left unconnected, as the internal 6MHz clock is used in this application. 4. LCD display and driver The microcontroller is interfaced to the custom LCD display via a Philips PCF8576 display driver chip, using the serial I2C bus. The serial data is converted to parallel data to drive the display segments and backplanes. Since the display has 47 separate segments, and the driver can only drive 40 segments on each backplane, the display has 23 segments commoned to COM1, which is connected to the backplane #0 driver pin (BP0) and 24 segments commoned to COM2, which is connected to the backplane #1 driver pin (BP1). The value of resistor R16 determines the clock rate for the display, a value of 150 kilohms giving a clock frequency of about 100 kHz. The interconnections between the segment driver output pins of the display driver and the segments of the display are chosen for ease of programming, with each of the four 7-segment digits and its associated decimal point being connected such that the data bits to drive its segments all reside in the same display driver data byte.

QBW ASSEMBLY LOAD CELL PREPARATION Install 4 off M4 x 25 hex head screws, each with an M4 lock nut, into the 4 tapped holes in the corners of the bottom frame. Verify load cell capacity, mark top frame with unit capacity. Verify load cell wiring colours. Note the direction and location of the arrow on the load cell. See detail drawing. Ensure that metal spacer is fitted between top of load cell and underside of top frame. Attach load cell to both frames using 2 off M6 x 16 hex socket screw, shakeproof washer and flat washer on each frame. These must be tightened as much as possible without stripping the threads. Isolate shield wire with heat-shrink tubing if this is not already done. Install the M4 x 50 pan head underload screw through the top frame into the threaded hole in the centre of the bottom frame, with an M4 locking nut between the frames. Adjust screw so head is just clear of top frame and lock into position with nut against top of bottom frame. LOAD CELL TO BASE All cables should be run under the load cell assembly. Connect load cell to PCB assembly at CONN3:

S

@

Normal Alternate Black pin 1 Red Green pin 2 Blue White pin 3 Green Red pin 4 White Shield Pin 5 Shield

ecure the load cell wires with plastic tie wrap or P clip to unused pillar near frame.

Adam Equipment Company 2004 16


Model Load Cell

Capacity PCB Links

No Load Display Counts

Full Load Display Counts

Span (FL – NL)

Min Max Min Max Min Max QBW 1.5 3kg SB3* -7620 -3380 11460 19940 19080 23320 QBW 3 5kg SB1 & SB3 -10070 -6730 4960 11640 15030 18370 QBW 6 10kg SB1 -8210 -4790 7180 10600 15390 18810 QBW 15 20kg SB1 -10670 -6530 7960 12100 18630 22770 QBW 30 35kg SB1 -11470 -6930 8960 13500 20430 24970 * For QBW 1.5 it is necessary to change C16 from 10nF to 100nF. This can be done by replacement or by putting 100nF in parallel with the standard 10nF. INITIAL TEST Apply mains power supply to unit and turn on. Check battery voltage is 6.2 to 6.7V and increasing. Observe the LED, it may be red if the battery is discharged or green if the battery has a full charge. When power is removed it will flash red as the voltage disappears. Place pan support and pan on the top frame. Press [On] to turn on scale. New PCB’s will detect that this is the first time the scale is active. The display will show the A/D counts. Acceptable A/D counts ranges at no load are shown in the table above. Place a mass on the scale. The number should become more positive. With full capacity on the scale the A/D counts should be between the values shown above. Apply the full load to each corner of the pan in turn and adjust the corresponding overload screw until its head just touches the underside of the top frame. Lock in position with the lock nut against the top of bottom frame. Move the full load to the centre of the pan and verify that none of the four overload stops are touching the top frame and that the clearance is equal on each screw. Remove the load and verify that the head of the underload screw is clear of the top frame.


Remove all mass, Press [Cal] key and hold for 3 seconds to initiate calibration. Display shows “C 0 ”. Press [Cal] key again and release. Display will show “tArE”. The display will then show the mass to be used, e.g. “ C 6 kg” for 6kg mass. Place this mass on the platform. Press the [Cal] key again. Scale will calibrate then show the mass value. Remove the mass, Verify the scale returns to zero. Turn off the scale then turn it back on again after a few seconds. Verify the calibration is still the same. Turn the scale off and remove the power supply connector.

LOAD CELL ASSEMBLY

M4 X 50 PH Screw

M4 Hex Nuts

M4- 25 Hex head (4)with locking nut

Top Frame

Note Large Holes forAccess to mounting screws

Small holes for pan support

Bottom Frame

Note Small (4mm) holes for mounting

Note Large Holes to clear foot

M6 Flat WasherM6, Shakeproof Washer

M6 X 16 Hex Socket Cap Screw4 sets of hardware in total

Cable


Manufacturer’s Declaration of Conformity

This product has been manufactured in accordance with the harmonised European standards, following the provisions of the below stated directives:

Electro Magnetic Compatibility Directive 89/336/EEC

Low Voltage Directive 73/23/EEC

Adam Equipment Co. Ltd.

Bond Avenue Denbigh East Estate

Milton Keynes, MK1 1SW United Kingdom

FCC COMPLIANCE This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment. The equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instruction manual, may cause harmful interference to radio communications. Operation of this equipment in a residential area is likely to cause harmful interference in which case the user will be required to correct the interference at his own expense. Shielded interconnect cables must be employed with this equipment to insure compliance with the pertinent RF emission limits governing this device. Changes or modifications not expressly approved by Adam Equipment could void the user's authority to operate the equipment.


ADAM EQUIPMENT is an ISO 9001:2000 certified global organisation with more than 30 years experience in the production and sale of electronic weighing equipments. Products are sold through a world wide distributor network -supported from our company locations in the UK, USA and SOUTH AFRICA. The company and their distributors offer a full range of Technical Services such as on site and workshop repair, preventative maintenance and calibration facilities. ADAM’s products are predominantly designed for the Laboratory, Educational, Medical and Industrial Segments. The product range can be classified as follows:

− Analytical and Precision Laboratory Balances − Top Loading Scales for Educational establishments − Counting Scales for Industrial and Warehouse applications − Digital Weighing/Check-weighing Scales − High performance Platform Scales with extensive software features including parts counting, percent weighing etc. − Digital Electronic Scales for Medical use − Retail Scales for price computing

Adam Equipment Co. Ltd.

Bond Avenue Milton Keynes

MK1 1SW UK

Phone:+44 (0)1908 274545 Fax: +44 (0)1908 641339

e-mail:

[email protected]

Adam Equipment Inc. 26, Commerce Drive

Danbury, CT 06810 USA

Phone: +1 203 790 4774 Fax: +1 203 792 3406

e-mail:

[email protected]

Adam Equipment S.A. (Pty) Ltd. P.O. Box 1422

Kempton Park 1620 Johannesburg

Republic of South Africa

Phone +27 (0)11 974 9745 Fax: +27 (0)11 392 2587

e-mail:

[email protected]

© Copyright by Adam Equipment Co. Ltd. All rights reserved. No part of this publication may be reprinted or translated in any form or by any means without the prior permission

of Adam Equipment.

Adam Equipment reserves the right to make changes to the technology, features, specifications and design of the equipment without notice.

All information contained within this publication was to the best of our knowledge timely,

complete and accurate when issued. However, we are not responsible for misimpressions which may result form the reading of this material.

The latest version of this publication can be found on our Website.


Visit us at www.adamequipment.com

mailto:[email protected]



http://www.adamequipment.com/

qbw scale - adam equipment usa...@adam equipment company 2004 3 n scale range = 1.5 kilograms...

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