Ultima MOS-5 Detector
24
4.7 Calibration
MSA recommends that the Ultima MOS-5 Intelligent Sensor be calibrated 1 hour after start-up,
and again 24 hours after initial start-up, and that the calibration be checked at least every 90
days to ensure system integrity of this 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.
MSA recommends that a calibration schedule be established and followed. A logbook should
also be kept, showing calibration dates and dates of sensor replacement.
4.7.1 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 1.5 mA output
signal and disabling the warn and alarm relays, if present. This will also prevent activation of
the remote relay contacts when using an MSA readout/relay display module with the Ultima
MOS-5 Intelligent Sensor. Please see section 9.3.3 for more information on the analog output
values.
To enter Calibration Mode, place the magnet over the MSA logo on the cover of the unit (Figure
4) and hold it there until “
AC
” (Figure 14) appears on the display (about 10 seconds). The
display will flash the remaining sensor life (Section 4.7.3) for a few seconds. Ensure that the
sensor is seeing clean air during this time.
Figure 14: 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 15).
Figure 15: Calibration in Progress Mode
