Model S4000T
21
4.6 Calibration
General Monitors recommends that the Model S4000T Intelligent Sensor be
calibrated one hour after start-up, and again 24 hours after initial start-up, and that
the calibration be checked at least every ninety (90) days, to ensure system integrity.
General Monitors is not implying that the customer should expect problems with
sensor life or stability, but “frequent” calibration checks merely ensure the integrity of
the life protecting equipment.
The above statement is not intended to discourage the customer from checking
calibration more frequently. Frequent calibration checks are recommended for
environments that have problems, such as mud collecting on the sensor head,
sensors accidentally being painted over, etc.
General Monitors recommends that a calibration schedule be established and
followed. A log book should also be kept showing calibration dates and dates of
sensor replacement.
4.6.1 Calibration Procedure
If Hydrogen Sulfide (H
2
S) gas is suspected to be present, it will be necessary to
purge the sensor environment with clean air.
Entering Calibration Mode automatically disables the alarm circuits by sending a
1.5mA output signal and disabling the Warn and Alarm relays, if present. This will
also prevent activation of the remote relay contacts when using a General Monitors
Readout/Relay Display Module with the Model S4000T.
To enter Calibration Mode, place the magnet over the GM Logo on the cover of the
unit (Figure 12) and hold it there until “
AC
” (Figure 27) appears on the display (about
ten seconds). The display will flash the Remaining Sensor Life (see Section 4.6.3) for
a few seconds. Ensure that the sensor is seeing clean air during this time.
Figure 27 Automatic Calibration Mode
Apply the calibration gas concentration to the sensor (50% FS of the desired range of
H
2
S). The display will change from “
AC
” (Automatic Calibration) to “
CP
” (Calibration
in Progress) indicating that the sensor is responding to the calibration gas (Figure
28).
Figure 28 Calibration in Progress Mode