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6.2. Span Calibration
1) Apply a SPAN gas to the sensor cell input and wait 2 minutes for the cell to
stabalize. Observe that the LCD display value increases and stabalizes.
2) Hold a magnet to the magnetically activated CAL/TEST switch.
3) Observe the LCD display and verify the value jumps 2 or 3 PPM below the
desired SPAN calibration value then slowly increases to the SPAN calibration gas
value. When the display reaches the SPAN value also observe that the display now
blinks the SPAN value. This indicates the SPAN parameters for the sensor cell have
been saved in memory.
4) Remove the magnet from the CAL/TEST switch.
5) During SPAN calibration of the sensor electronics, the unit evaluates the amplified
gas sensor cell output to determine that the value is between 1.50 VDC and 3.00VDC
at the test point TP1. If the voltage is not between these two values a
sensor
calibration error “E”
will appear in the left digit of the LCD display as the LCD
begins to flash the full scale value. The “
E”
error indicates that the sensor cell is
defective and should be replaced. The
“E”
will remain
ON
until the sensor cell is
replaced and re-calibrated properly. The PLC Monitor System Master Station will
also be notified that a calibration error has occurred at this sensor.
Note: There is no adjustment available to bring the amplified sensor cell output
back into the proper range. Replace the sensor cell or the entire unit.
6) Remove the SPAN gas from the sensor cell and observe that the LCD display
returns to zero or to the ambient value.
