Detcon CXT-IR - Manual (Page 25)

Model CXT-IR
concentration is 50% of range. If a span gas containing the recommended concentration is not available, other
concentrations may be used as long as they fall between 5% and 95% of range. However, any alternate span
gas concentration value must be programmed via the Set AutoSpan Level menu before proceeding with
AutoSpan calibration. Follow the instructions a) through f) below for AutoSpan calibration.
a) Verify that the AutoSpan level is equal to the calibration span gas concentration. (Refer to View Sensor
Status in Section 3.4.1.) If the AutoSpan level is not equal to the calibration span gas concentration, adjust
the AutoSpan level as instructed in Section 3.3.2AutoSpan.
b) From normal operation, enter calibration mode by holding the programming magnet over PGM1 for 3
seconds.
NOTE
The "
◄"prompt will show that the magnetic switch is activated during the 3 second hold
period.
c) The display will then scroll PGM1=Zero PGM2=Span. Hold the programming magnet over PGM2 for
3 seconds to execute AutoSpan (or allow to timeout in 5 seconds if AutoSpan is not intended). The ITM
will then scroll Apply XX % Gas.
NOTE
Upon entering calibration mode, the Modbus™ status register bit 14 is set to signify the
sensor is in-calibration mode. This bit will remain set until the program returns to normal
operation.
d) Apply the span calibration test gas for combustible gas sensors at a flow rate of 200-500cc/min (500cc/min
is the recommended flow rate). As the sensor signal begins to increase the display will switch to flashing
XX
reading as the ITM shows the sensorꞌs as found response to the span gas presented. If it fails to meet
the minimum in-range signal change criteria within 2 minutes, the display will report Range Fault twice
and the ITM will return to normal operation, aborting the AutoSpan sequence. The ITM will continue to
report a Range Fault until a successful calibration is completed.
Assuming acceptable sensor signal change, after 1 minute the reading will auto-adjust to the programmed
AutoSpan level. The ITM then reports the following messages: Remove Gas.
e) Remove the span gas source and calibration adapter. The ITM will report a live reading as it clears toward
0. When the reading clears below 10% of range, the ITM will display Span Complete and will revert to
normal operation. If the sensor fails to clear to less than 10% in less than 5 minutes, a Clearing Fault will
be reported twice and the ITM will return to normal operation, aborting the AutoSpan sequence. The ITM
will continue to report a Clearing Fault until a successful calibration is completed.
f) AutoSpan calibration is complete.
NOTE
If the sensor fails the minimum signal change criteria, a Range Fault will be declared and
the Range Fault bit will be set on the Modbus™ output.
NOTE
If the sensor fails the clearing time criteria, a Clearing Fault will be declared and the
Clearing fault bit will be set on the Modbus™ output.
CXT-IR Instruction Manual Rev. 1.6 Page 21 of 44