Analytical Industries GPR-3500 MO Portable Oxygen Analyzer - Manual (Page 23)

Advanced Instruments Inc.
23
Sampling
GPR-3500MO Oxygen Portable oxygen purity analyzer requires positive pressure to flow the sample gas by the sensor to measure the
oxygen concentration in a sample gas. If not available see Pressure & Flow section.
Note: Prematurely zeroing the portable oxygen purity analyzer can cause the portable oxygen purity analyzer to display a negative
reading in both the ZERO and SAMPLE modes.
Procedure:
1. Following calibration the portable oxygen purity analyzer returns to the SAMPLE mode after 30 seconds.
2. Selecting the desired sampling mode is not applicable with this single range analyzer - auto or manual are the same.
3. Use metal tubing to transport the sample gas to the portable oxygen purity analyzer.
4. 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 1/8” male NPT to tube adapter, and,
the NPT end is taped and securely tightened into the mating male quick disconnect fittings which mate with the female fittings on
the portable oxygen purity analyzer
5. Assure there are no restrictions in the sample line.
6. 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 2 SCHF is recommended
7. For sample gases under atmospheric or slightly negative pressure an optional sampling pump is recommended to draw the sample
into the portable oxygen purity analyzer. Generally, no pressure regulation or flow control device is involved.
8. Caution: If the analyzer is equipped with an optional sampling pump and is intended for use in both positive and
atmospheric/slightly negative pressure applications where a flow meter valve is involved – ensure the valve is completely open
when operating the sampling pump. Refer to the Pressure & Flow section above.
9. Assure the sample is adequately vented for optimum response and recovery – and safety.
10. Allow the oxygen reading to stabilize for approximately 10 minutes at each sample point.
To avoid erroneous oxygen readings and damaging the sensor:
¾ 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).
¾ Assure there are no restrictions in the sample or vent lines
¾ Avoid drawing a vacuum that exceeds 14” of water column pressure – unless done gradually
¾ Avoid excessive flow rates above 5 SCFH which generate backpressure on the sensor.
¾ Avoid sudden releases of backpressure that can severely damage the sensor.
¾ Avoid the collection of particulates, liquids or condensation collect on the sensor that could block the diffusion of oxygen into the
sensor.
¾ If the portable oxygen purity 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.
Standby
¾ The portable oxygen purity analyzer has no special storage requirements.
¾ The sensor should remain connected during storage periods.
¾ Store the portable oxygen purity analyzer with the power OFF.
¾ If storing for an extended period of time, charge before operating.