Xnx Ec Sensor Operational Life; Zero And Span Calibration For Mpd Sensors - Honeywell XNX Quick Start Manual

result in a short-term negative drift in the instrument's reading. These are
most likely to be noticed during calibration with dry or cylinder gas.
When calibrating Hydrogen Sulfide cartridges the following should be taken into
account while following the procedure in Section 6.1.1:
1. To zero the sensor, use a compressed gas cylinder of 20.9%Vol oxygen
(not Nitrogen). Do not use background air.
2. If a span calibration is to be performed, the span calibration gas should be applied
to the sensor immediately after the zeroing procedure. Do not allow the sensor to
return to ambient air conditions.
6�1�4 XNX EC Sensor Operational Life
Typical life of a toxic gas sensor is dependent on the application, frequency and amount
of gas exposure. Under normal conditions, with a 3 month visual inspection and 6 month
test/re-calibration, the toxic sensor has an expected life equal to or greater than the
lifetime as listed below:
• 18 months for Chlorine and Chlorine Dioxide sensors.
• 12 months for Ammonia and Hydrogen Fluoride sensors. (See Ammonia note
below.)
• 24 months for Oxygen and other toxic sensors.
cAutIoN
Oxygen deficient atmospheres (less than 6%V/V) may result in inaccuracy of
reading and performance.
Note:
Ammonia electrochemical cells are reliable and suitable for applications where no
background concentration of ammonia exists. Under these conditions the cells
are expected to operate for 12 to 24 months.
These ammonia cells are of the consumptive type. Their operating life can be
adversely affected by continuous or excessive exposure to ammonia, or by
prolonged exposure to high temperatures and moisture.
To ensure continued detection availability, it is recommended that the detectors are
regularly bump tested and a relevant cell replacement program be implemented.
6�1�5 Zero and Span Calibration for MPD Sensors
cAutIoN
Before initial calibration allow, the detector to stabilize for 30 minutes after
applying power. When in zero and span calibration mode, the current output from
the detector is inhibited (default 3mA) to avoid false alarms.
This section describes how to calibrate MPD flammable sensors fitted to the XNX.
The calibration adjustments are made on the XNX's display and gassing is performed
at the sensor. This may be locally or remotely located.
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XNX Universal Transmitter Quick Start Guide