Chapter 3
Alarm
Alarm allows you to set an alarm level that will be triggered if the instrument’s
reading goes above the setpoint. However, the alarm functioning is
determined by the logging interval. The alarm will turn ON only if the average
concentration over the logging interval exceeds the set point. If the logging
interval is too long and the concentration exceeds the set point and stays at
that level, the alarm will not turn ON until after the logging interval has
passed. Likewise, the alarm will not stop until after the concentration has
dropped below 5% of the threshold and after the logging interval has passed.
The Alarm is dependent on the logging interval. For the DustTrak
to alarm as soon as the Alarm Setpoint is exceeded, the logging
interval must be set as low as possible (i.e., 1 second or
2 seconds). If a long test duration does not permit setting such a
short logging interval, use the STEL alarm instead. The STEL is
always based on 1 second concentrations and is independent of
the logging interval. For more details on the STEL alarm, see
section below on STEL.
In Survey mode, the alarm is dependent on the time constant.
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