Detcon CX-DM - Manual (Page 20)

Model CX-DM
AutoSpan consists of entering Calibration Mode and following the displayed instructions. The display will ask
for the application of span gas in a specific concentration. The applied gas concentration must be equal to the
calibration gas level setting. The factory default setting and recommendation for span gas 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 100% of range. However, any alternate span gas
concentration value must be programmed via the Set AutoSpan Level menu before proceeding with AutoSpan
calibration.
1. Verify that the AutoSpan Level is equal to the Calibration Span Gas Concentration. (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 3.4.3.
2. 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.
3. The display will 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 scroll ‘Apply XX ppm Gas’.
4. Apply the span calibration test gas for toxic 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 sensor
ꞌs "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" for 1 minute.
NOTE
Ambient air should be used to calibrate O
2
deficiency sensors as long as the oxygen
concentration is confirmed to be 20.9%. There is no need to apply a flow of gas.
5. 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’.
6. 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.
NOTE
When calibrating O2 deficiency sensors, there is no requirement to clear to <5% of range.
The sensor will return to normal operation immediately after span adjustment.
7. 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.
CX-DM Instruction Manual Rev. 1.3 Page 16 of 40