Analytical Industries GPR-3100 Series Oxygen Purity Analyzer - Manual (Page 29)

Advanced Instruments Inc.
5 Operation
GPR-3100 Rev 2/05 22
16. The analyzer returns to the SAMPLE mode after 30 seconds.
17. Before disconnecting the span gas line and connecting the sample gas line, restart if necessary the
flow of sample gas and allow it to flow for 1-2 minutes to purge the air inside the line.
18. Disconnect the span gas line and replace it with the purged sample gas line.
19. Wait 10-15 minutes to ensure the reading is stable and proceed to sampling.
20. Once calibrated, the analyzer is ready for Sampling.
Sampling
Procedure Following Span Calibration
1. Reconnect the sample gas line as described above (the analyzer returns to the SAMPLE
automatically).
2. Caution: Assure that the vent line is connected to a ¼” or larger tube and is vented to atmosphere,
with the magnification associated with the use of suppressed ranges even the slightest amount of
backpressure will adversely affect the oxygen reading.
3. Set the sample gas pressure between 5 and 30 psig (100 psig maximum to retain the precision
control of the flow from the flow control valve).
4. Set the sample gas flow rate to approximately 2 SCFH.
5. Advance the cursor (*) on the SAMPLE menu to select either AUTO or MANUAL RANGING
6. Press ENTER to accept the selection.
7. Allow the oxygen reading to stabilize, the analyzer would typically stabilize in 5-15 minutes.
Display Negative (Readings)
The analyzer provides the user with the option to choose whether they wish to display negative readings.
This feature is useful if the user prematurely zeroes the analyzer either inadvertently or knowingly during
a quick start situation.
Advance the cursor (*) on the MAIN MENU to SYSTEM and press ENTER to accept the selection.
From the above SYSTEM menu advance the cursor (*) to DISPLAY NEGATIVE and press ENTER to
select/toggle between ON and OFF (default). The default or OFF selection causes the analyzer to
automatically correct the reading displayed and the zero offset once a negative reading (signal) has been
detected for a constant 90 minutes.
Note: Prematurely zeroing the analyzer can cause the analyzer to display a negative reading in both the
ZERO and SAMPLE modes.
Depending on the magnitude of the zero offset and the oxygen value of the sample gas, the analyzer
may only display a reading of 00.0 (if the zero offset value exceeds the oxygen value of the gas). A
constant 00.0 reading suggests repeating the zero calibration procedure with DISPLAY NEGATIVE ON
(allowing sufficient time for the reading to stabilize) before concluding there is a problem with the
analyzer.