Detcon CX-DM - Manual (Page 18)

Model CX-DM
combustible gas levels, re-calibration should be considered. Unless otherwise specified, span adjustment is
recommended at 50% of the full scale range.
To enter calibration mode hold the magnet over PGM1 for 3 seconds. If the sensor is experiencing a fault
condition the "
►" prompt will not appear until the fault(s) have been displayed. When the ITM enters
calibration mode the display will scroll Pgm1=Zero Pgm2=Span twice before returning to normal mode
(about 5 seconds).
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.
3.3.1 AutoZero
The AutoZero function will zero the sensor. AutoZero should be performed periodically or as required.
AutoZero should be considered after periods of over-range target gas exposure. Local ambient air can be used
to zero calibrate a toxic gas sensor as long as it can be confirmed that it contains no target or interference
gasses. If this cannot be confirmed then a zero air or N
2
cylinder should be used. Pure N
2
must be used for
zero calibration of the O
2
deficiency sensors.
Material Requirements:
• MicroSafe™ Programming Magnet (Detcon PN 327-000000-000)
• Splash Guard with integral Cal Port (Detcon P/N 613-120000-700) and Calibration Wind Guard
(Detcon PN 613-120000-700 ) -or-
• Threaded Calibration Adapter (Detcon PN 943-000006-132)
• Zero Air cal gas (or use ambient air if no target gas is present) (Detcon PN 942-001123-000 )
• Nitrogen 99.99% (Detcon P/N 942-640023-100)
NOTE
The zero gas source may be zero air or N
2
for toxic sensors, but must be pure N
2
(99.99%)
for O
2
deficiency sensors.
NOTE
The Calibration Wind Guard must be used when the Splashguard Adapter with integral Cal
Port is used. Failure to use the Calibration Wind Guard may result in an inaccurate
AutoZero calibration.
1. Toxic sensors, if the ambient air is known to contain no target gas content, can be used for zero
calibration. If a zero gas cal cylinder is going to be used, attach the calibration adapter and set flow
rate of 200-500cc/min (500cc/min is the recommended flow rate) and let sensor purge for 1 to 2
minutes before executing the AutoZero. For O
2
deficiency sensors, apply N
2
at a set flow rate of
500cc/min for 3 to 5 minutes before executing AutoZero.
2. From Normal Operation, enter Calibration Mode by holding the programming magnet over PGM1 for
3 seconds. The "
◄" prompt will show that the magnetic switch is activated during the 3 second hold
period. The display will then scroll Pgm1=Zero Pgm2=Span. Hold the programming magnet over
PGM1 for 3 seconds once the "
◄" prompt appears to execute AutoZero (or allow to timeout in 5
seconds if AutoZero is not desired).
NOTE
The "
◄" prompt will show that the magnetic switch is activated during the 3 second hold
period.
NOTE Upon entering calibration mode, the Modbus™ status register bit 14 is set to signify the
CX-DM Instruction Manual Rev. 1.3 Page 14 of 40