Detcon FP-700 - Manual (Page 19)

Model FP-700
FP-700 Instruction Manual Rev. 3.0 Page 15 of 40
3.3 Normal Operation
In normal operation, the ITM Display continuously shows the current sensor reading, which will normally
appear as “ 0 ”. Once every 60 seconds the LED display will flash the sensor’s measurement units and gas
type (i.e. % LEL). If the sensor is actively experiencing any diagnostic faults, a “Fault Detected” message will
flash on the ITM display every 60 seconds. At any time, while the unit is in “Fault Detected” mode, PGM1 or
PGM2 can be swiped to prompt the sensor to display the list of the active faults.
In normal operation, the 4-20mA current output corresponds with the present gas concentration and full-scale
range. The RS-485 Modbus™ serial output provides the current gas reading and fault status on a continuous
basis when polled.
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
AutoZero calibration.
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: