Zero-Point Offset Adjustment - Sartorius CP64 Service Manual

Zero point offset adjustment
R
GND
IC6 Pin6
Aut_5027.jpg
Caution!
R
J3
J2
J1
Aut_5027.jpg
The offset adjustment adapts the weighing system to the internal A/D converter.
You may need to adapt the A/D converter:
- after replacing the strain gauge measuring spring
- after replacing the main PCB
- when the sensitivity of the balance/scale cannot be adjusted (not even using the
service software) and error code „Err 02" is displayed.
There are two ways of adapting the converter:
1. with a digital voltmeter
2. using the service software (SARTOCAS, PSION Server)
1. Adapting the A/D Converter using a Digital Voltmeter:
- Open balance/scale
- Reconnect balance/scale to mains power
- Unload the weighing pan, use a digital voltmeter to measure IC6 Pin 6 against
GND (see figure on the left)
Open the solder bridges and measure the ground at IC6 Pin 6. Depending on the
voltage displayed, open or close the solder bridges in accordance with the chart (see
next page). If the adjustment cannot be carried out through the solder bridges, an
adjustment resistance (R, see fi gure left) determined with a decade resistor can be set
when the solder bridges of the offset are open.
The converter output must be within the range of the between
-250 mV and -650 mV!
After replacing the main PCB, it may be necessary to transfer the existing
adjustment resistance (R) to the new PCB.
Umeas (V)
(solder bridges are open)
-0.212...+0.153
+0.153...+0.518
+0.518...+0.883
+0.883...+1.249
2. Adapting the A/D Converter Using the Service Software (SARTOCAS /PSION):
- Activate the BPI Mode
- Use the service software in the „Diagnosis" menu to check the output level
(modulation) of the A/D converter
Caution!
Opening or closing solder bridges (J1 - J3) must change the converter output to
within the range of 5% to 14%!
J1 J2
Closed Open
Open Closed
Closed Open
Closed Closed
| 17
J3
Open
Open
Closed
Closed