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2.1
the auxiliary alarm setpoint. Press the appropriate
button to obtain the desired reading on the digital
display.
5. When no changes have been made for 5 sec-
onds, the Auxiliary LED goes out, the CAL LED
blinks, and the digital display indicates the cali-
bration gas concentration. Press the appropriate
button to change the calibration gas concentra-
tion as required.
6. When no changes have been made for 5 sec-
onds, the controller automatically returns to the
Normal operating mode.
7. Record the new values for future reference.
NOTE
The alarm setpoints, calibration gas concentration,
and calibration data are stored in non-volatile
memory and are retained in the event of a power
loss. However, if power is interrupted while
performing the Setpoint Adjustment or Calibration
procedure, the entire procedure must be repeated
when power is restored.
CALIBRATION
Various factors affect the time interval between
periodic recalibrations. Exposure to certain
contaminants in the air, accumulation of contaminants
on the filter, or an extended period of normal
operation can cause changes in sensitivity. Since
each application is different, the length of time
between regularly scheduled recalibrations can
vary from one installation to the next. In general, the
more frequently a system is checked, the greater the
reliability. Calibration
must
be performed:
— When a new system is initially put into service
— When the sensing element is replaced
— If a transmitter or controller used in conjunction with
the sensor is replaced
— When the hydrophobic filter is cleaned or replaced.
The following calibration schedule is recommended
when placing a new sensor into operation and will
ensure reliable operation in most applications:
1. One hour after power-up
2. One
week
later
3. Every 30 days thereafter, or as determined by the
needs of the specific application.
IMPORTANT
To ensure adequate protection, the H
2
S detection
system must be calibrated on a regularly
scheduled basis.
Loss of sensitivity can be caused by various fac-
tors. One common cause is by clogging of the
hydrophobic filter by dirt, oil, paint, etc. Problems
of this nature will not be detected by the system’s
diagnostic circuitry. While performing detec-
tor calibration, the operator should examine the
hydrophobic filter of the sensor. If it cannot be
properly cleaned, it should be replaced.
The detector must be calibrated using hydrogen
sulfide mixed with either air or nitrogen. For best
results, a calibration gas concentration equal
to the high alarm setpoint or 50% of full scale is
recommended.
NOTE
If the sensing element is being replaced, refer to
the “Sensing Element Replacement” section (under
“Maintenance”) in this manual for information
regarding replacement and calibration of the
sensor.
CALIBRATION PROCEDURE
The H
2
S detection system can be calibrated using
either of two methods:
1.
Transmitter calibration (if a transmitter is
used).
This method of calibration can be per-
formed by one person. All adjustments are made
at the transmitter. Calibration of certain transmit-
ter models requires removing the enclosure cover,
therefore, the hazardous area must be de-classi-
fi ed.
When transmitter calibration is performed, an
initial calibration of the controller must be per-
formed in addition to the transmitter calibration.
This calibration of the controller is not the same
as “2. Controller Calibration” described below.
It involves setting factory default calibration val-
ues in the controller that will ensure accuracy
when used in conjunction with a properly cali-
brated transmitter. Since these default values do
not change, the procedure does not need to be
repeated with subsequent transmitter recalibra-
tions. This controller calibration is accomplished
by momentarily entering the Sensor Replacement
mode. Upon entering the Sensor Replacement
mode, the controller automatically sets the fac-
tory default controller calibration values. (Follow
the procedure described in the “Setting Controller
Default Values” section.)
