Detcon PI-700 - Manual (Page 21)

Model PI-700
PI-700 Instruction Manual Rev. 2.5 Page 17 of 54
magnet over PGM2 for 3 seconds to execute AutoSpan (or allow to timeout in 5 seconds if AutoSpan is
not intended). The ITM will then scroll “Apply XX ppm Gas”.
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) Apply the span calibration test gas for VOC gas sensors at a flow rate of 200-500cc/min using the in-line
humidifying tube (200cc/min is recommended). As the sensor signal begins to increase the display will
switch to flashing “XX“reading as the ITM shows the sensor’s “as found” response to the span gas
presented. If it fails to meet the minimum in-range signal change criteria within 2½ minutes, the display
will report “Range Fault” twice and the ITM will return to normal operation, aborting the AutoSpan
sequence. The ITM will continue to report a “Range Fault” and will not clear the fault until a successful
AutoSpan is completed.
Assuming acceptable sensor signal change, after 1 minute the reading will auto-adjust to the programmed
AutoSpan level. During the next 30 seconds, the AutoSpan sequence checks the sensor for acceptable reading
stability. If the sensor fails the stability check, the reading is re-adjusted back to the AutoSpan level and the
cycle repeats until the stability check is passed. Up to three additional 30-second stability check periods are
allowed before the unit reports a “Stability Fault” twice and the ITM will return to normal operation, aborting
the AutoSpan sequence. The ITM will continue to report a “Stability Fault” and will not clear the fault until a
successful AutoSpan is completed.
If the sensor passes the stability check, the ITM reports a series of messages:
“Span OK”
“Sensor Life XXX%”
“Remove Span Gas”
d) Remove the span gas source and calibration adapter. The ITM will report a live reading as it clears toward
“0”. When the reading clears below 10% of range, the ITM will display “Span Complete” and will revert
to normal operation. If the sensor fails to clear to less than 10% in less than 5 minutes, a “Clearing Fault”
will be reported twice and the ITM will return to normal operation, aborting the AutoSpan sequence. The
ITM will continue to report a “Clearing Fault” and will not clear the fault until a successful AutoSpan is
completed.
NOTE: When calibrating sensors where there are high levels of VOC gases in the ambient
background, use Zero Air or N
2
to assist clearing to <10% of range.
e) The AutoSpan calibration is complete.
NOTE 1: Upon entering the calibration menu, the 4-20mA signal drops to 2mA and is held at
this level until the program returns to normal operation.
NOTE 2: If the sensor fails the minimum signal change criteria, a “Range Fault” will be
declared and a “Fault Detected” message will be displayed alternately with the sensor’s
current reading. The 4-20mA output will be taken to 0mA and the ‘Range Fault’ fault bit will
be set on the Modbus™ output.
NOTE 3: If the sensor fails the stability criteria, a “Stability Fault” will be declared and a
“Fault Detected” message will be displayed alternately with the sensor’s current reading. The
4-20mA output will be taken to 0mA and the ‘Stability Fault’ fault bit will be set on the
Modbus™ output.