VAT 653 Series - Zero Adjust

Series 65 INSTALLATION
963283EA Edition 2019-05-03 47/
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4.8.2 Zero Adjust
Zero Adjust allows for the compensation of the sensor offset voltage.
When Zero Adjust is performed the current value at the sensor input is equated to Zero.Adjust Target
Pressure.
In case of a 2 sensor system both sensor inputs will be adjusted.
Note: A maximum offset voltage of +/- 1.4 V can be compensated.
To execute a zero adjust, the zero adjust have to be enabled (see chapter above).
Parameter Description
Zero Adjust.Sensor
Selection
Select the sensor for the zero adjust:
• Sensor 1 + 2
• Sensor 1
• Sensor 2
Zero Adjust.Target
Pressure
Normally this parameter is set to 0 in case the process chamber is fully
evacuated (which means pressure value is nearly 0). If not you can align
the sensor value to a known pressure. In this case set Target Pressure
to the current pressure.
Note: Target Pressure is in the unit of pressure, see chapter «Scaling of
Pressure and Position Values»
Zero Adjust.Execute
Start the zero adjust by set
Execute
to 1
At this moment offset value will be calculated and Sensor x.Value =
Target Pressure. The resulting offset value can be read on parameter
Sensor x.Offset Value [SFS]
Clear the offset values by setting Execute to 2
The result of clearing the zero adjust: Sensor x.Offset Value [SFS] = 0.0
Sensor 1.Enable
Sensor 2.Enable
0: It’s not possible to execute a zero adjust. A present offset
value is ignored.
1: It’s possible to execute a zero adjust. A present offset value
is respected.
Sensor 1.Offset Value
[SFS]
Sensor 2.Offset Value
[SFS]
Value which will be subtracted from measured sensor value
The value is related to sensor full scale (0.1 means 10% of sensor full
scale)
Parameter location:
CPA RS232
Pressure Sensor->Zero Adjust
Pressure Sensor->Sensor 1->Zero Adjust
Pressure Sensor->Sensor 2->Zero Adjust
Pressure Sensor->Sensor 1->Zero Adjust
Pressure Sensor->Sensor 2->Zero Adjust
Refer to “RS232 setup commands” for
details.
Performing a zero adjust:
1. Wait until process chamber is evacuated and sensor signal is not shifting anymore. Do not
perform Zero Adjust as long as pressure gauge voltage is shifting otherwise incorrect pressure
reading is the result. Refer to manual of sensor manufacturer for warm up time.
2. Set parameter Sensor Selection
3. Set parameter Target Pressure (Zero Adjust->Target Pressure, not the Target Pressure for
pressure control)
4. Set parameter Execute = 1
5. Check parameter Actual Pressure if the pressure is shifted as expected