Advanced Instruments Inc.
4.
Advance the reverse shade cursor using the ARROW keys to highlight DEFAULT SPAN.
5.
Press the ENTER key to select the highlighted menu option.
The following display appears
100.0
OUTPUT SPAN OFFSET
PRESS UP OR DOWN
TO CHANGE VALUE
ENTER TO SAVE
MENU TO RETURN
6.
Compute the adjustment value as described in Appendix B or consult the factory. The true adjustment value must
be determined empirically by trial and error. Adjust the initial adjustment value for additional percent errors.
7.
Press the ENTER key to advance the underline cursor right or press the MENU key to advance the underline cursor
left to reach to the desired digit of the OUTPUT SPAN OFFSET value.
8.
Press the ARROW keys to enter the OUTPUT SPAN OFFSET value.
9.
Repeat steps 9 and 10 until the complete OUTPUT SPAN OFFSET value has been entered.
10.
Save the adjustment by pressing the ENTER key or abort by pressing the MENU key
Note: The number 100 is the default value. With OUTPUT SPAN set at 100, no adjustment is made to the 1V signal.
To increase the 1V signal increase the OUTPUT SPAN above 100. To decrease the 1V signal, decrease the OUTPUT
SPAN below 100.
Sampling a Gas
GPR-1200 Oxygen Analyzer requires a positive pressure to flow the sample gas across the sensor to measure the
oxygen concentration in a sample gas. If a positive sample pressure is not available see the option of using a sample
pump as described above.
Procedure
Following calibration, the analyzer will return to the SAMPLE mode.
1.
Select the desired sampling mode - auto or manual – as described above.
2.
Use metal tubing to transport the sample gas to the analyzer
3.
The main consideration is to eliminate any air leaks which can affect oxygen measurements.
4.
For sample gases under positive pressure, the user must provide a means of controlling the inlet pressure
between 5-30 psig.
5.
For sample gases under atmospheric or slightly negative pressure, an optional sampling pump is recommended to
push the sample through the sensor housing. Generally, when using a pump, no pressure regulation or flow
control device is involved. However, a flow meter upstream of analyzer is recommended to ensure that the sample
flow is adequate.
6.
Assure the sample is adequately vented for optimum response and recovery – and safety.
7.
Allow the oxygen reading to stabilize for approximately 10 minutes at each sample point.
8.
Avoid drawing a vacuum that exceeds 14” of water column pressure – up to 40 “if done gradually
9.
Avoid flow rates above 5 SCFH which may generate backpressure on the sensor.
10.
Avoid sudden releases of backpressure that can severely damage the sensor.
11.
Avoid the collection of particulates, liquids or condensation on the sensor that could block the diffusion of oxygen
into the sensor.
12.
If the analyzer is equipped with an optional integral sampling pump (positioned downstream of the sensor) and a
flow control metering valve (positioned upstream of the sensor), completely open the flow control metering valve
to avoid drawing a vacuum on the sensor and placing an undue burden on the pump.
27
