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

sudden increase in ambient humidity can result in a short-term positive drift in the
instrument's reading. A sudden decrease in ambient humidity can 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 8.1.1:
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.

8.1.4 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:
• 12 months for Ammonia and Hydrogen Fluoride sensors. (See Ammonia
note below.)
• 24 months for Chlorine Dioxide, 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.

8.1.5 Zero and Span Calibration for MPD Sensors

CAUTION
Extended or frequent exposure to elevated concentrations of combustible gases
may affect sensor sensitivity. Verify sensor performance by frequent calibration.
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.
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XNX Universal Transmitter Quick Start Guide