Time-stamped alarms are similar to digital alarms,
except that a counter is used to provide an accurate timestamp of
when a triggering condition occurs, rather than just the time the
variable was polled. Time-stamped alarms can only be associated
with a single digital variable.
An alarm's variables are polled at the rate set by
[Alarm]ScanTime, however, the timer value is used to define the
time associated with a change of state.
You can use one of three types of counter or timer
to record the triggering of time-stamped alarms:
counter. A continuous counter is read in the unit to determine
the sequence in which the alarms are triggered. The alarms are
sorted based on the value of the counter when the alarm was
triggered (the exact time is not recorded).
counter. If your unit supports a millisecond counter, you can
program a counter (in the unit) to count (in milliseconds) for 24
hours, and then reset (at midnight). The value of this timer
variable (in the unit) is read to determine the exact time when the
alarm was triggered.
timer. Using a LONGBCD timer, you can log the exact time when a
time-stamped alarm becomes active. This variable is read, along
with the alarm tag when the alarm activates.