Model FP-700
FP-700 Instruction Manual Rev. 5.1 Page 18 of 46
Caution: Off-scale readings may indicate a flammable concentration
3.4 Calibration Mode (AutoZero and AutoSpan)
3.4.1 AutoZero
The AutoZero function is used to zero the sensor. Local ambient air can be used to zero calibrate the sensor as
long as it can be confirmed that it contains no combustible gases. If this cannot be confirmed then a zero air
cylinder should be used.
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 cal gas or use ambient air if no combustible gas is present.
NOTE 1: The zero gas source should have a normal background concentration of 20.9% O2.
Pure Nitrogen gas standards should not be used or errors may result.
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
a) If the ambient air has is known to contain no combustible gas content, then it can be used to zero calibrate.
If a zero gas cal cylinder is going to be used then attach the calibration adapter and set flow rate of 200-
500cc/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 3-4
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 3-4 seconds once the “◄” prompt appears to execute AutoZero (or allow to timeout in 10 seconds
if AutoZero is not desired).
NOTE: 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.
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% LEL.
NOTE: Before performing AutoSpan Calibration, verify that the AutoSpan level matches the
span calibration gas concentration as described in Section 3.5.3Set AutoSpan Level.
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