Instrutech VGC301A, User Manual, Page: 32 / 34

Instruction Manual VGC301A Controller
InstruTech, Inc.
Page 30
9 Service
9.1
Calibration
Every InstruTech gauge is calibrated prior to shipment using nitrogen (N
2
). However, you can calibrate the instrument by
adjusting zero and span (atmosphere) using the procedure described previously in the “Setup and Operation” section (also
see User Interface Map). Zero and span (atmosphere) calibration affect the displayed value and the output signal. Zero
calibration optimizes performance of the gauge when operating at a low pressure range of 1 x 10
-4
Torr to 1 x 10
-3
Torr. If
your minimum operating pressure is higher than 1 x 10
-3
Torr, it is not normally necessary to perform calibration at zero and
thus span calibration should be adequate. If you are able to evacuate your system to below 1 x 10
-4
Torr, it is always a good
practice to check and set zero if necessary. This will also improve performance in cases where gauge contamination is
causing higher readings than 1 x 10
-4
Torr even though the system has been evacuated to below 1 x 10
-4
Torr. Care should
be exercised when using gases other than nitrogen (N
2
) / air.
9.2 Maintenance
In general, maintenance is not required for your InstruTech gauge and controller. Periodic performance checks may be
done by comparing the gauge to a known reference standard.
9.3 Troubleshooting
Indication Possible Cause Possible Solution
Display is off / blank No power Check power supply & power cable
Readings appear very different from
expected pressure The process gas is different from the
gas used to calibrate the CVG101 gauge Correct readings for different gas thermal
conductivity. See section on using the gauge on
different gases
CVG101 gauge has not been calibrated
or has been calibrated incorrectly Check that zero and span are adjusted
correctly
Readings are noisy or erratic Loose cables or connections Check and tighten connections.
Contamination Inspect CVG101 for signs of contamination
such as particles, deposits, discoloration on
gauge inlet. Return to factory for possible
cleaning
Vibration Ensure gauge is not mounted where excessive
vibration is present
Gauge cannot be calibrated - zero and span
can’t be adjusted Contamination
Sensor failure for other cause
Return CVG101 to factory for possible cleaning
Replace CVG101 gauge
Setpoint does not actuate Incorrect setup Check setpoint setup
Display shows “Sensor Bad” Sensor wire damaged Replace CVG101 gauge
Display shows “overpressure” System pressure over 1000 Torr
Faulty electronics
Reduce pressure
Repair or replace VGC301 electronics
Atmospheric pressure reads too high and
can’t be set to correct value Contamination
Sensor wire damaged
Return CVG101 to factory for possible cleaning
Replace CVG101 gauge
Atmospheric pressure reads too low and
can’t be set to correct value Sensor wire damaged
Contamination
Replace CVG101 gauge
Return CVG101 to factory for possible cleaning