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 Precision Balances
Page 2
KERN 440…N
KERN 440…A
Version 4.0 4/2008
440…N-SH-e-0840
GB
KERN 440…N / 440…A
Version 4.0 4/2008
Service Manual
Electronic Precision Balances
2 440…N-SH-e-0840
Table of Contents
1 Features.......................................................................................................................3
2 Calibration Procedure (CAL) .....................................................................................3
3 Internal Calibration Procedure (Linearity Adjustment) ...........................................4
3.1 Readout of the Internal Counts.............................................................................................4
4 Display Segment Test .............................................................................................. 5
5 Functional Block Diagram / Description...................................................................5
5.1 Functional Block Diagram.....................................................................................................5
5.2 Function Description.............................................................................................................6
6 Trouble Shooting........................................................................................................7
7 To Replace PCB..........................................................................................................8
8 To Replace Load Cell Assembly................................................................................9
9 Schematics................................................................................................................ 10
10 Components Layout .................................................................................................12
440…N-SH-e-0840 3
1 Features
• Full Tare
• Memory function with indicator
• Stable indicator
• Negative value indication
• Two types of Digital Auto Calibration
• Solder pads to prevent end-user internal calibration
• RS232 interface, printing function
• Custom scale by going through SET manual
- Multiple serial interface modes
- Different communication baud rates selectable
- Auto off enable / disable
- Zero tracking enable / disable
- Multiple calibration weight selectable
- Backlight selectable
- Animal weighing
• Low battery indicator
• Auto off function (battery mode only)
• AC adaptable
• Display segment test function
• Overload protection
• Optional rechargeable battery
• Pre-Tare function
2 Calibration Procedure (CAL)
1. Turn balance on and allow the unit to acclimatize and stabilize for 2 hours.
2. Select the calibration weight according to the operating manual with [Print],
[Mode/Cal] and [Set/M] keys.
3. Press and hold the [Mode/Cal] key until the display shows a flashing weight reading.
The flashing weight reading indicates the correct weight that must be placed on the
weighing pan.
4. Gently place the correct calibration weight on the center on the weighing pan. With the
display still flashing, press the [Set/M] key.
5. The display will now show [Cal F] and then return to normal operating mode. The
calibration is complete when the display correctly shows the weight that is placed on
the weighing pan while the display has stabilized.
6. Remove the calibration weight and press the [TARE] key to reset the zero point.
In case [CAL E] is displayed instead of [CAL 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 top housing of the scale.
2. Connect J3 on the main board by soldering the pads together.
3. Place scale on a hard level surface. With weighing pan installed, turn scale on.
Display shall show the internal counts.
4. The internal counts shall fall in the range from 55 000 to 85 000. In case out of this
range, connect J10 left side or right side to increase or reduce the reading.
Connecting or disconnecting pads on J7, J8 or J9 can fine tune the reading.
5. Press [Set/M] key once. Display will show [CAL 0] and then the required calibration
weight. Place the corresponding calibration weight on the center of the weighing plate.
Press [Set/M] again while the weight placed on the weighing pan is stable.
6. Display will now show [CAL 1] and then the next calibration weight. Place the
corresponding calibration weight on the weighing plate. Repeat this step until display
shows [CAL F]. Remove all weights from weighing pan.
7. Turn the scale off and disconnect J3.
8. Turn scale on and check the accuracy at different weight.
9. Install the top housing of the scale.
In case [CAL E] is display instead of [CAL F], this indicates a calibration procedure error
or wrong weight applied for calibration.
Turn the scale off and then on and repeat the procedure.
3.1 Readout of the Internal Counts
For example:
Without number
In that case the internal count is 66 063
With number (here 3)
You have to set this number
before the value
In that case the internal count is 321 580
4 440…N-SH-e-0840
Loading...