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has been successful without having to return to the receiver. The receiver’s display will also
provide this information when the operator returns to the receiver once all sensors have been
calibrated. This method of calibration permits a single operator to carry out all the calibration
by setting the instrument to RUN CALIBRATION and exposing the sensor to the calibration
gas without opening the sensor/transmitter or having to make adjustment at either the receiver
or the sensor/transmitter.
Calibration sources are connected to the sensor such that during calibration the gas feed to
the sensor is completely controlled. Calibration is aborted if:
• A power failure results in loss of power to the sensor/transmitter
• A level alarm occurs between selecting RUN CALIBRATION and activating the
sensor’s magnetic switch
• The “watchdog timer” detects a microprocessor malfunction during calibration
Refer to section 5.0 for a detailed description of the calibration process.
3.2.2.12 Security and Safety
3.2.2.12.1 Password
The receiver may be configured so that entry of a password is required to gain
entry to the SETUP menu (refer to section 3.2.2.8). This may be desirable to
prevent accidental or malicious change of programmed information.
3.2.2.12.2 Watchdog Timer
A processor “watchdog timer” monitors processor operation and determines if
a failure has occurred (refer to section 3.2.2.8). Processor malfunction during
calibration results in the calibration being aborted. Should this occur, the old
calibration data is retained while the display indicates information regarding the
nature of the problem.
3.2.2.12.3 Power Failure
A loss of power results in two modes of operation:
• Units with battery backup - normal operation continues uninterrupted
• Units without battery backup - the units will shut down and start up
automatically, without alarms, when power is restored
Units with battery backup will automatically switch to battery power in the event
of a main power failure and the unit will continue to operate in its normal mode.
3.2.2.13 Battery Operation
During normal AC powered RUN mode operation, the battery condition (if so equipped) is
checked every hour on the hour. The state of the battery may be seen by checking the SETUP-
CONFIGURE-INSTRUMENT-BATTERY STATUS menu selection.
Under certain conditions, the display backlight will be shut off to conserve power or signal a
faulty battery. These conditions are:
• If an AC power failure is detected
• If AC power is present but the battery is determined to be faulty
The battery will provide power for the unit for a minimum of 24 hours in the event of a power
failure. Refer to section 4.4.2.13 for more information on backup battery operation status.
3.2.2.14 Operational Alarms
Operational alarms may occur during the monitoring of the ambient air in the RUN mode. The
alarms automatically appear in a quadrant of the LCD display, the location depending on which
sensor channel caused the alarm condition.
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