Analytical-industries GPR-1200 ATEX Portable Trace PPM Oxygen Analyzer Manuel d'utilisateur télécharger pdf (Page 25)

9. Press the ARROW keys to enter the OUTPUT SPAN OFFSET value.

10. Repeat until the complete OUTPUT SPAN OFFSET value has been entered.

11. Save the adjustment value by pressing the ENTER key or abort by pressing the MENU key.

12. The system returns to the SAMPLING mode.

Sampling

The sensor is exposed to sample gas that must flow or be drawn through the analyzer’s internal sample system.

As illustrated above, the GPR-1200’s internal sample system includes:

¾ 1/8” tube fittings for the inlet and outlet

¾ flow control metering valve

¾ 4-way SAMPLE/BYPASS bypass valve

¾ Stainless steel sensor housing with an o-ring seal to prevent the leakage of air

¾ Tee to combine the sample and bypass lines

¾ Flow indicator common to bypass and sample lines

Flow rates of 1-5 SCFH cause no appreciable change in the oxygen reading. However, flow rates above 5 SCFH generate

backpressure and erroneous oxygen readings because the diameter of the integral tubing cannot evacuate the sample gas at

the higher flow rate. A FLOW upstream of the sensor controls the flow rate of the sample gas which is displayed by the flow

indicator downstream of the sensor. A flow rate of 2 SCFH or 1liter per minute is recommended for optimum performance.

Application Pressure - Positive:

A flow control metering valve positioned upstream of the sensor controls the sample flow rate between 1-5 SCFH. If necessary,

a pressure regulator (with a metallic diaphragm is recommended for optimum accuracy, the use of diaphragms of more

permeable materials may result in erroneous readings) upstream of the flow control valve should be used to regulate the inlet

pressure between 5-30 psig.

Application Pressure - Atmospheric or Slightly Negative:

For accurate ppm range oxygen measurements, an optional integral sampling pump is positioned downstream of the sensor to

draw the sample from the process, by the sensor and out to atmosphere.

Caution: If the analyzer is equipped with an optional integral sampling pump (positioned downstream of the sensor),

completely open the flow control metering valve (positioned upstream of the sensor) to avoid drawing a vacuum on the sensor

and placing an undue burden on the pump.

Procedure:

1. Review the end of the Span Calibration procedure beginning with step #28 and section on Pressure & Flow in section 3.

2. Select the desired sampling mode - auto or if manual, the range that provides maximum resolution.

3. Use metal tubing to transport the sample gas to the 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,

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Analytical-industries GPR-1200 ATEX Portable Trace PPM Oxygen Analyzer Manuel d'utilisateur Page 25