XNX Universal Transmitter
Section 3 - Calibration
110
Warning: When the transmitter is placed in Inhibit Mode, alarms are silenced. This will prevent an
actual gas event from being reported. Inhibit Mode must be limited to testing and maintenance only.
Exit Inhibit Mode after testing or maintenance activities.
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 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.
!
The Gas Calibration menu is for both zero and span calibrations.
This section describes how to calibrate MPD ammable sensors
tted to the transmitter. The calibration adjustments are made on the
transmitters display. Gassing is performed at the sensor, which may be
locally or remotely located.
The following equipment is required:
• Flow housing (Honeywell part number 1226A0411)
• Test gas
• Regulator
Note: Use the zero gas and span gas at about the same humidity levels to avoid erroneous cell
responses.
!
1. If there is a weatherproof cap on the MPD, remove it.
2. Fit the ow housing onto the MPD.
Figure 213. Flow housing
Figure 214 shows the ow housing accessory tted to the
MPD.
Figure 214. MPD with Flow Housing
3. Connect the ow housing (using either gas pipe) to the
regulated cylinder containing a known concentration of the
target gas at approximately the sensor alarm point, e.g., 50%
LEL methane in air.
Warning: As some test gases are hazardous, exhaust the ow housing outlet to a safe area.
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