Analytical Industries GPR-35 Oxygen Analyzer - Manual (Page 22)

Advanced Instruments Inc.
22
Procedure Air Calibration Sensor Flow Housing :
Not recommended unless user confirms the ambient air or atmosphere surrounding
the analyzer is not contaminated.
1. Review the above Span Calibration procedure and the following instructions
before proceeding.
2. Access the interior of the analyzer by removing the four (4) screws securing the
front panel.
3. Unscrew the knurled lock nut connecting the cable to the sensor.
4. Disconnect and remove the female plug (including the knurled lock nut) molded
to the cable from the male receptacle attached to the sensor.
5. Unscrew the sensor from the threaded hole in the sensor flow housing.
6. Immediately re-connect and insert the female plug (including the knurled lock
nut) molded to the cable from the male receptacle attached to the sensor.
7. Re-tighten the knurled lock nut connecting the cable to the sensor.
8. The sensor is now exposed to ambient air, connected to the analyzer electronics
and ready for calibration.
9. With the sensor exposed to ambient air – allow the reading to stabilize before
adjusting the SPAN potentiometer.
10. After the reading stabilizes, turn the SPAN potentiometer ½ turn at a time until
the LED display reads the 20.9 oxygen content of ambient air.
11. Caution: Turning the potentiometer more the ½ turn recommended does not
allow the electronics sufficient time to keep pace with the adjustment. And since
adjustments are rarely made in one consecutive turn – there is a real possibility
that the 2
nd and 3 rd part of the adjustment could unknowingly be based on “values that have not stabilized” thereby
resulting in an inaccurate calibration.
12. Reinstall the sensor as follows:
13. Unscrew the knurled lock nut connecting the cable to the sensor.
14. Disconnect and remove the female plug (including the knurled lock nut) molded to the cable from the male receptacle
attached to the sensor.
15. Screw the sensor into the threaded hole in the sensor flow housing.
16. Immediately re-connect and insert the female plug (including the knurled lock nut) molded to the cable from the male
receptacle attached to the sensor.
17. Re-tighten the knurled lock nut connecting the cable to the sensor.
18. Replace the SENSOR panel or close the door of the analyzer.
19. Wait 5-10 minutes to ensure the reading is stable and proceed to sampling.
Sampling
The GPR-35 is designed for in-situ ambient or area monitoring and has no sample system
because the sensor is intended to be exposed directly to the surrounding ambient
atmosphere which it is sampling and to operate at atmospheric pressure, however, slightly
positive pressure has minimal effect on accuracy.
Applications situations may dictate that the sample be transported from a semi-sealed area to a safe area where the analyzer is
located. In these cases the analyzer can be readily adapted to include optional pumps, tubing and connection fittings.