For each trigger, two limits are typically defined: the operate limit to assert the
event, and the release limit - to release the event when the operate condition reverts.
The release condition is the reversed operate condition (see Table 4-4).
Table 4-4 Setpoint Conditions
Operate condition Release condition Limits
Greater or equal (over
operate limit)
Less or equal (under release
limit)
Both limits active
Less or equal
(under operate limit)
Greater or equal (over release
limit)
Both limits active
Equal Not equal Release limit not used
Not equal Equal Release limit not used
ON OFF Both limits not used
OFF ON Both limits not used
NEW min/max value n/a Both limits not used
A separate release limit can be used to provide hysteresis (dead band) on event
operation. When the trigger parameter value is between the operate and release
limits, the event status does not change. If the event was asserted before entering the
dead band, it is still asserted while the parameter remains within the band.
NOTE
When using operate conditions over limit/under limit, the release limit must be always
specified for the event to be released. If the user does not want to provide hysteresis, the
release limit may be set the same as for the operate limit.
Logical Triggers
Logical triggers are the parameters that can be checked by testing their status. Those
are external status parameters, pulse events, and internal events that are asserted by
the instrument.
For logical triggers, the following operate conditions can be used:
- ON
- OFF
- NEW (Min/Max log)
A NEW condition can be applied to Min/Max log parameters, to check whether the
new minimum or maximum is logged for the parameter from the last time it was
checked.
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