Det-Tronics R8471NH34001,2,3 Single Channel Gas Controller, NH3 - Manual (Page 21)

19 95-8529 1.1
CALIBRATION PROCEDURE
NOTE
While in the Calibrate mode, all controller outputs
are inhibited, the CAL LED is illuminated, and the
current output goes to a preset level (adjustable
from 0 to 20 ma, with a default value of 4.0 ma).
Calibration typically requires two people, one person
at the controller and another at the sensor. The actual
calibration adjustments are made automatically by the
microprocessor in the controller.
NOTE
An accumulation of contaminants on the
screen or hydrophobic filter can block the flow
of gas to the sensor, adversely affecting its
performance. Before starting the calibration, the
operator should examine the sensor screen or
filter (if used). A dirty hydrophobic filter should
be replaced. The hydrophobic filter should be
clean and squarely seated in the housing. The
hydrophobic filter should not be used with the Cl
2
sensor.
1. Be cer tain that the controller is properly
programmed for the calibration gas time. Reprogram
the controller if required.
NOTE
The recommended calibration time is five
minutes. Shorter calibration times are acceptable
based on the discretion of the operator.
2. Check the gauge on the gas cylinder to be sure that
there is enough gas for a 5 minute calibration. If
the cylinder runs out before 5 minutes, an improper
calibration will result.
IMPORTANT
Sensors must be calibrated with a gas
concentration that is equal to 50% full scale
value: 5 ppm for Cl
2
sensors, 50 ppm for SO
2
sensors, 10 ppm for NO
2
sensors.
3. Be sure that only clean air is present at the sensor.
(The microprocessor begins taking zero readings
immediately upon entering the Calibrate mode.)
If the possibility of background gases exists,
purge the sensor with clean air to ensure accurate
calibration.
4. To enter the calibrate mode, depress and hold the
Reset button until the CAL LED is illuminated and
the digital display starts to flash (approximately 9
seconds).
5. When the Zero calculations are complete (30
seconds minimum), the digital display stops flashing
and reads “00”.
6. Apply the calibration gas to the sensor. The digital
display starts to flash, and the value indicated
on the display rises. The bar graph display also
indicates the level of gas at the sensor, but does not
flash.
7. When the microprocessor has completed the Span
adjustment, the digital display stops flashing.
NOTE
If the sensor output stabilizes before the end of
the programmed calibration time, the controller
will accept the span value and exit the Calibrate
mode early.
8. Remove the calibration gas. When the gas level
falls below the lowest alarm setpoint, the controller
automatically exits the Calibrate mode. All outputs
and indicators return to normal operation.
If the operator fails to complete the calibration, if the
sensitivity of the sensor has deteriorated to the extent
that calibration cannot be successfully completed, or
if the 10 minute calibration time limit expires before
completion of the calibration, a calibration fault
(“F2X” status) will be generated and the controller
will automatically revert back to the former calibration
settings.
If the microprocessor determines that the sensor cell
is approaching the end of its useful life, “F10” will be
indicated on the digital display. This does not indicate
a system malfunction, but is intended simply to make
the operator aware of this condition. A successful
calibration can still be performed. Press Reset after
completing calibration to clear the display.
IMPORTANT
If a calibration attempt should fail for any reason,
do not repeat the calibration. Either wait 30 days
before calibrating, or replace the sensor cell with
one that has been free of gas for at least 30 days
and then calibrate.