13
Gas Connections:
The GPR-2500/2500MO with its standard flow through configuration is designed for positive pressure samples and
requires connections for incoming sample and outgoing vent lines. Zero and span inlet ports are offered as part of
the optional sample systems. The user is responsible for calibration gases and the required components, see
below.
With the pressure regulated to between 5-30 psig, 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
indicator with an integral metering valve upstream of the sensor is recommended as a means of controlling the
flow rate of the sample gas. A flow rate of 2 SCFH or 1 liter per minute is recommended for optimum performance.
Caution: 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).
Procedure:
1. Caution: Do not change the factory setting until instructed to do in this manual.
2. Designate one of the bulkhead tube fittings as the VENT and the other SAMPLE.
3. Regulate the pressure as described in Controlling Pressure & Flow above.
4. Connect a 1/8” vent line to the compression fitting to be used for venting the sample.
5. Connect a 1/8” ZERO, SPAN or SAMPLE line to the fitting designated SAMPLE.
6. If equipped with optional fittings and/or sample system, connect the ZERO and SPAN gas lines.
7. Allow gas to flow through the transmitters and set the flow rate to 2 SCFH.
