Honeywell XNX, Technical Manual

Page: 96 / 200

XNX Universal Transmitter
Section 3 - Calibration 94
3.2.4 Zero and Span Calibration of XNX EC Hydrogen
Sulfide ( H
2
S) Sensors
Caution: Before initial calibration, allow the sensor to stabilize for 30 minutes
after applying power. When in zero and span calibration modes, the current
output from the sensor is inhibited (default 2mA) to avoid false alarms.
Caution: Recalibrate if the temperature of local environment has varied by
more than ±15°C from the temperature of calibration.
Hydrogen Sulfide sensors can be affected by extreme humidity
changes� A 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 3�2�2 �
1� To zero the sensor, use a compressed gas cylinder of
20�9%Vol oxygen (not nitrogen)� Do not use background
air�
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�
Warning:
Long-term exposure (> 20 minutes) to concentrations exceediing the
full-scale range of the sensor can cause it to lose sensitivity. The ouput of the
sensor may then decrease in value even though high levels of toxic gas are still
present. Before re-calibrating the transmitter, verify the absence of gas.
3.2.5 705/705HT Calibrating
For complete calibration and configuration information, see the
Type 705 Operating Instructions (P/N: 00705M5002)�
3.2.6 Sensepoint/Sensepoint HT Calibrating
For complete calibration and configuration information, see the
Sieger Sensepoint Technical Handbook (P/N: 2106M0502)�
3.2.7 Calibrating the Searchpoint Optima Plus
Complete calibration and configuration information can be
found in the Searchpoint Optima Plus Operating Instructions
(P/N:2108M0501)� If properly installed and maintained, the
Searchpoint Optima Plus sensor will not require routine
calibration� This is due to the inherent stability of the IR
absorption process and the unit’s fully compensated optical
configuration�
1� From the Calibration menu, select the Gas Calibration option�
Figure 204. Calibration menu