Detcon PI-700 0-500ppb - Manual (Page 17)

Model PI-700 0-500ppb
PI-700 0-500ppb Instruction Manual Rev. 0.0 Page 13 of 53
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 0ppb VOC’s. If this cannot be confirmed then a zero air
(zero ppm VOC) cylinder should be used. Optionally, a Carbon Scrubber can be used to provide a VOC-free
gas sample for zero calibration.
Material Requirements:
-Detcon PN 327-000000-000 MicroSafe™ Programming Magnet
-Detcon PN 942-001123-000 Zero Air cal gas (or use ambient air if no target gas is present).
a) For VOC sensors, if the ambient air is known to contain no target gas content 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. Connect the Cal Gas to the Sample Port as shown in
Figure 12. Ensure that there is a 6” Vent Tube connected to the ‘T’ before the Humidifying Tube.
Connect the humidifying Tube to the Sample Port. Adjust the Flow Regulator on the Cal Gas Cylinder to
about 1000cc/min, then adjust the Rotameter flow rate to 500cc/min. Allow the 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 “V” 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 “S” 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 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.
Material Requirements:
-Detcon PN 327-000000-000 MicroSafe™ Programming Magnet
-Detcon Span Gas (See Detcon for Ordering Information). Recommended span gas is 50% of range with
Isobutylene in air or N
2
balance (250ppb IsoButylene).
-Detcon P/N 985-241100-321 In-Line Humidifying Tube 24"