Analytical Industries GPR-7500 AIS Trace PPM Hydrogen Sulfide Analyzer - Manual (Page 28)

Advanced Instruments, Inc.
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6. The default setting of 100 illustrates no adjustment to the analog output signal. Adjust the initial value to
above 100 to increase the 20 mA analog signal value or decrease it below 100 to decrease the 20 mA
analog signal.
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 desired digit. After entering the digit press ENTER and the 20 mA
signal will adjust to the new value.
9. If the 20 mA signal still does not match with 20 mA signal, repeat steps 7 through 8 the 20 mA matches
with the display..
10. Save the adjustment value by pressing the ENTER key or abort by pressing the MENU key.
The system returns to the SAMPLING mode.
Sampling
GPR-7500 AIS H2S Transmitter requires a positive pressure to flow the sample gas across the sensor to
measure the H2S concentration in a sample gas.
Procedure
Following calibration, the transmitter automatically returns to the SAMPLE mode.
1. Select the desired sampling mode - auto or if manual, the range that provides maximum resolution – as
described above.
2. Use metal tubing to transport the sample gas to the transmitter.
3. The main consideration is to eliminate air leaks which can affect oxygen measurements above or below
the 20.9% oxygen concentration in ambient air - ensure the sample gas tubing connections fit tightly
into the sample input port.
4. For sample gases under positive pressure, the user must provide a means of controlling the inlet
pressure between 5-30 psig and the flow of the sample gas between 1-5 SCFH, a flow rate of 1-2 SCHF
is recommended
5. For sample gases under atmospheric or slightly negative pressure, an optional sampling pump is
recommended to push the sample 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. Note: To avoid erroneous oxygen readings and damage to the sensor, do not place your finger over the
vent (it pressurizes the sensor) to test the flow indicator when gas is flowing to the sensor. Removing
your finger (the restriction) generates a vacuum on the sensor and may damage the sensor (voiding the
sensor warranty).
9. Assure there are no restrictions in the sample or vent lines
10. Avoid drawing a vacuum that exceeds 14” of water column pressure – unless done gradually
11. Avoid excessive flow rates above 5 SCFH which may generate backpressure on the sensor.
12. Avoid sudden releases of backpressure that can severely damage the sensor.
13. Avoid the collection of particulates, liquids or condensation on the sensor that could block the diffusion
of oxygen into the sensor.
100.0
OUTPUT SPAN OFFSET
PRESS UP OR DOWN
TO CHANGE VALUE
ENTER TO SAVE
MENU TO RETURN