Detcon IR-700 - Manual (Page 19)

Model IR-700
IR-700 Instruction Manual Rev. 3.1 Page 15 of 40
3.4 Calibration Mode (AutoZero and AutoSpan)
3.4.1 AutoZero
The AutoZero function is used to set the sensor’s zero baseline. Local ambient air can be used to zero
calibrate the sensor as long as it can be confirmed that it contains no combustible hydrocarbon gases. If this
cannot be confirmed then a zero air or pure N2 cylinder should be used. The same AutoZero procedure
applies for the CO2 version sensor.
Material Requirements:
 Detcon PN 327-000000-000 MicroSafe™ Programming Magnet
 Detcon PN 613-120000-700 700 Series Splash Guard with integral Cal Port and Calibration Wind
Guard (P/N 943-000000-000) -OR-
 Detcon PN 943-000006-132 Threaded Calibration Adapter
 Detcon PN 942-001123-000 Zero Air (or N2) cal gas, or use ambient air if no combustible gas is
present.
a) If the ambient air is known to contain no combustible hydrocarbon gas content, it can be used to calibrate
zero. If a zero air or N2 gas cal cylinder is going to be used then attach the calibration adapter and set flow
rate of 200 cc/min and let sensor purge for 1-2 minutes before executing the AutoZero.
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. 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 1: Upon entering Calibration Mode, the 4-20mA signal drops to 2mA and is held at this
level until the program returns to normal operation. Modbus™ Status Register bit 14 is also set
to signify when the sensor is in-calibration mode.
NOTE 2: 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.
c) The ITM will display the following sequence of text messages as it proceeds through the AutoZero
sequence:
Zero Cal. . .Setting Zero. . . Zero Saved (each will scroll twice)
d) Remove the zero gas and calibration adapter, if applicable.
3.4.2 AutoSpan
The AutoSpan function is used to span calibrate the sensor. Span adjustment is recommended at 50% of range
for LEL and CO
2
sensors. Follow the same procedure for both. The gas Factor Table (Section 3.5.4 Set Gas
Factor Table 2) should be used for Methane and for Heavy Hydrocarbon gas.
NOTE: Before performing AutoSpan Calibration, verify that the AutoSpan level matches the
span calibration gas concentration as described in Section 3.5.2Set AutoSpan Level.