Detcon PI-700 - Manual (Page 19)

Model PI-700
PI-700 Instruction Manual Rev. 2.5 Page 15 of 54
3.4 Calibration Mode
3.4.1 AutoZero
The AutoZero function is used to zero the sensor. Local ambient air can be used to zero calibrate a VOC 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.
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 target gas is present).
 Detcon P/N 942-640023-100
Nitrogen 99.99%
 Detcon P/N 985-241100-321
In-Line Humidifying Tube 24"
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.
a) For VOC sensors, if the ambient air is known to contain no target gas content, then it can be used for zero
calibration. If a zero gas or N
2
cal cylinder is going to be used, be sure to use in-line humidifying tube to
present cal gas with correct ambient humidity level. 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
seconds. Note, the “◄” prompt will show that the magnetic switch is activated during the 3 second hold
period. The display will then scroll “PGM1=AutoZero …PGM2=AutoSpan”. 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: 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
a) Remove the zero gas and calibration adapter, if applicable.
3.4.2 AutoSpan
The AutoSpan function is used to span calibrate the sensor. Unless otherwise specified, span adjustment is
recommended at 50% of range. This function is called “AUTO SPAN”.
NOTE: Before performing AutoSpan Calibration, verify that the AutoSpan level matches the
span calibration gas concentration as described in Section 3.5.2 Set AutoSpan Level.