Calibration - GasTech GTA-4100R Operator's Manual

3.5 Calibration

The only calibration that needs to be performed at the GTA-4100R is for a catalytic sensor with no field
amplifier (using the GTA-4100R internal amplifier). Follow this procedure:
1. Switch the required channel to be calibrated into Isolate mode using the Isolate switch on the front
panel.
2. The display will invert, the alarms will be deactivated and the 4-20mA output will drop to 2mA. While
the channel is in Isolate no alarms from that channel will activate.
NOTE: When in Isolate mode the dead bands are removed so you can get an exact calibration, and view
any small change in sensor output.
CAUTION: The visual and audible alarm indicators and relays are inactive during isolation mode and will
not indicate any hazardous condition on that channel that may occur while in Isolate mode
3. Apply zero grade air to the sensor and allow the sensor to stabilize.
4. Slowly adjust the "Zero" pot on the front panel of the GTA-4100R until the display shows "0" or the
required value.
5. Apply the span gas to the sensor and allow it to stabilize.
6. Slowly adjust the "Span" pot on the front panel of the GTA-4100R till the display displays the required
value.
7. Remove the gas and apply zero grade air to the sensor again and allow the reading to stabilize.
8. Once the sensor has reached "0" or the required value you can bring the channel out of isolation, this
will reactivate the alarms.
Page 34 © 2008 GasTech Australia Pty Ltd