KERN ECB Manuel utilisateur

KERN & Sohn GmbH

Ziegelei 1

D-72336 Balingen

E-Mail: info@kern-sohn.com

Tel: +49-[0]7433-9933-0

Fax: +49-[0]7433-9933-149

Internet: www.kern-sohn.com

GB Service Manual

Electronic Platform Scales Page 2

KERN ECB / ECE

Version 2.0 4/2008

ECB/ECE-SH-e-0820

GB KERN ECB / ECE

Version 2.0 4/2008

Service Manual

Electronic Platform Scales

Table of Contents

1Features.......................................................................................................................3

2Calibration Procedure (CAL) .....................................................................................3

3Internal Calibration Procedure (Linearity Adjustment) ...........................................4

4Display Segment Test ..............................................................................................5

5Functional Block Diagram / Description...................................................................6

5.1 Functional Block Diagram.....................................................................................................6

5.2 Function Description.............................................................................................................7

6Trouble Shooting........................................................................................................8

7To Replace PCB..........................................................................................................9

8Schematics................................................................................................................10

9Components Layout.................................................................................................12

2 ECB/ECE-SH-e-0820

ECB/ECE-SH-e-0820 3

1 Features

•Zero weight function

•Negative value indication

•Low battery indicator

•Auto zero

•Display segments test function

•Auto off function in battery mode - enable/disable (only ECB)

•Overload protection

•Overload indication

•Digital span calibration

•Digital internal calibration

•Operated by 6 x AA size alkaline batteries

•Rechargeable battery as option

•Zero tracking - enable/disable (only ECB)

•Backlight - 3 modes (only ECB)

2 Calibration Procedure (CAL)

1. Turn scale on and allow the unit to acclimatize and stabilize for 10 minutes.

2. Press and hold the [Tare] key for approx. 3 seconds. Display will show [CAL] and then

the required calibration weight.

3. Gently place the correct calibration weight on the center on the weighing pan.

4. Wait until the display shows [ F] and then return to normal weighing mode

automatically.

5. Remove the calibration weight and press the [TARE] key to reset the zero point.

In case [ E] is displayed instead of [ F], this indicates a calibration

procedure error. Turn the scale off and then on and repeat the procedure.

3 Internal Calibration Procedure (Linearity Adjustment)

1. Remove the bottom cover under the PCB of the scale.

2. Connect J1 on the main board by soldering the pads together.

4 ECB/ECE-SH-e-0820

3. Place scale on a hard level surface. Turn scale on. Display shall show the internal

counts.

4. The internal counts shall fall in the range from 3 000 to 6 000. In case out of this

range, remove the four screws from the main board and lift it to see the rear side

of the main board.

5. Connect J9 left side or right side to increase or reduce the reading.

Connecting or disconnecting pads on J5, J6 or J7 can fine tune the reading.

ECB/ECE-SH-e-0820 5

6. If the internal counts are within the range, press [ON/OFF] key once. Display will show

[CAL] and then the required calibration weight. Place the corresponding calibration

weight on the center of the weighing plate. Wait until display shows the next calibration

weight.

7. Repeat the above calibration procedure until display shows [ F].

8. Remove all weights from weighing pan and disconnect the power supply.

9. Disconnect J1 on the main board. Turn scale on and check the accuracy at different

weight.

10. Install the bottom cover of the scale.

In case [ E] is display instead of [ F], this indicates a calibration procedure error

or wrong weight applied for calibration.

Turn the scale off and then on and repeat the procedure.

4 Display Segment Test

Whenever the scale is power on, all segments of the LCD will be turn on for approx.

2 seconds. Check for any missing segment.

5 Functional Block Diagram / Description

5.1 Functional Block Diagram

6 ECB/ECE-SH-e-0820

digital signal

analog

signal

Microprocessor

Power control /

Regulator &

Low battery

detector

Keyboard

A/D Converter

Battery (6xAA)

Adaptor

Amplifier

4 Load cells

(Sensor)

L C D

ECB/ECE-SH-e-0820 7

5.2 Function Description

1. Load cell

This is the heart of the whole system. The load cell itself is arranged as a bridge.

The resistance change of the bridge elements is proportional to the load applied on

the load cell. Therefore, the output of the load cell is an analog signal, which is

proportional to the load applied on the scale.

2. Amplifier

The analog signal from the load cell is very small, of the order of micro-volt.

Hence, a linear and stable amplifier is applied to amplify the analog signal to an

appropriate level.

3. A/D Converter

In order for the analog signal can be input to the microprocessor, this part converts the

analog signal to its digital equivalent. The operation of the analog to digital converter

is using a SIGMA DELTA technique and under the control of the microprocessor.

4. Microprocessor

The microprocessor control all the functions of the scale, such as auto zero,

A/D conversion, timings, weight calculation, display, overload indication, low battery

indication, zero function, etc….

5. Display

This is the part where the weight is shown out on the LCD display in digital form.

The whole display is driven by the microprocessor.

6. Power Regulator and Low Battery Detector

This part contains the ON/OFF power control. In order for the external power can be

used by other parts of the scale, a regulator is used to regulate the supply.

A low battery detector is employed to make sure that the power supply is strong

enough for normal operation of the scale.

7. Keyboard

The keyboard provides on user interface. [On/Off] and [Tare] keys are employed to

operate the scale.

8 ECB/ECE-SH-e-0820

6 Trouble Shooting

Power on

↓

Full Segments?

If no display, check batteries / adaptor, keyboard / overlay, connection between

keyboard—main board, batteries / adaptor—main board.

If missing segments, check fixing of LCD, zebra connector under LCD.

↓

Display Zero?

If display [ LO], check battery>7.0V.

If display [ E] , check internal count.

↓

Proper readout?

If unstable reading, check weighing plate, overload stopper, load cell and

environmental conditions and stable table.

↓

Correct reading?

If not accurate, perform internal calibration.

If cannot reach full capacity, check weighing plate, overload stopper, load cell

and internal zero point.

If always zero, check internal zero point. Internal calibration if necessary.

↓

Normal operation.

ECB/ECE-SH-e-0820 9

7 To Replace PCB

1. Remove the bottom cover under the PCB of the scale.

2. Remove the four screws fixing the PCB and disconnect wires of keyboard, load cell

and battery/adaptor (backlight at ECB) from PCB. Replace a new PCB.

Connect wires of keyboard, load cell and battery/adaptor (backlight at ECB) to PCB

again. Assemble the screws fixing the PCB.

4. Perform internal calibration as described in section 3.

5. Assemble the bottom cover of the scale.

6. Check accuracy of scale at different weight.

ECB 10K10 ECB 20K20 ECB 50K50

weight tolerance weight tolerance weight tolerance

2.00 kg 0.02 kg 5.00 kg 0.04 kg 10.00 kg 0.10 kg

5.00 kg 0.02 kg 10.00 kg 0.04 kg 20.00 kg 0.10 kg

7.00 kg 0.02 kg 15.00 kg 0.04 kg 30.00 kg 0.10 kg

10.00 kg 0.02 kg 20.00 kg 0.04 kg 40.00 kg 0.10 kg

50.00 kg 0.10 kg

ECE 10K10 ECE 20K20 ECE 50K50

weight tolerance weight tolerance weight tolerance

2.00 kg 0.02 kg 5.00 kg 0.04 kg 10.00 kg 0.10 kg

5.00 kg 0.02 kg 10.00 kg 0.04 kg 20.00 kg 0.10 kg

7.00 kg 0.02 kg 15.00 kg 0.04 kg 30.00 kg 0.10 kg

10.00 kg 0.02 kg 20.00 kg 0.04 kg 40.00 kg 0.10 kg

50.00 kg 0.10 kg

7. Check other functions, such as Tare, Off and Auto-Off.

8 Schematics

10 ECB/ECE-SH-e-0820

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