QRAE II User Guide
Page 58
9.4 Replacing Sensors
Under normal operating conditions, sensors lose their original sensitivity after the
expected operating life and need to be replaced.
Warranties: The oxygen (O
2
), combustible gas (LEL), hydrogen sulfide (H
2
S) and
carbon monoxide (CO) sensors all have a 2-year warranty.
Replace a sensor when it fails to calibrate. If it fails to calibrate, retry calibrating it.
Check the QRAE II’s parameter settings, and check that the calibration gas is not beyond
its “Use by” date. For further details, refer to RAE Systems Technical Note TN-123,
“Special Diagnostic Modes For RAE Systems Instruments,” available at
www.raesystems.com.
When a CO or H2S sensor is saturated, the LCD gives you this message:
Xxx Fail
Turn off unit
Remove or
Replace sensor
Turn off the QRAE II and replace the sensor. Always recalibrate after replacing a sensor.
If the LEL sensor fails, the LCD indicates it like this:
CO: 0ppm
H2S: 0.0ppm
OXY: 20.9%
LEL: Fail
Instead of showing a reading, the word “Fail” appears. Replace the LEL sensor and
recalibrate the instrument.
If the oxygen sensor fails, there is no prompt. If you install a bad oxygen sensor, the
QRAE II gives a message of “Oxy not found” during startup diagnostics.
9.4.1 Sensor Locations
The sensors are located inside the front of the monitor.
See RAE Systems Technical Note TN-114, Sensor Specifications And Cross-
Sensitivities, for additional information, available at www.raesystems.com.
To replace a sensor:
1. Turn off the QRAE II.
2. Place the QRAE II face-down on a soft surface.
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