Setpoint #1 is factory preset to provide standard periodic data logs on a 15-
minute time basis. It is linked to the device clock and runs data logs #1 and
#2 at 15-minute boundaries of an hour.
Using Logical Expressions
Logical operators OR/AND are treated in a simplified manner. They have no
specific priority or precedence rules.
Any trigger condition bound to the logical expression by the OR operator and
evaluated as “true” will override any preceding condition evaluated as “false”.
Similarly, any trigger condition evaluated as “false” and bound by the AND
operator will override any condition evaluated before it as “true”.
To avoid confusion, it is recommended not to alternate different logical
operators in one expression. Instead, bring all conditions that use the same
logical operator together at one side of the expression, and the others - at
the opposite side.
To explicitly override all other conditions with the critical trigger, put it at the
end of the expression using the OR operator if you want the setpoint to be
operated anyway when the trigger condition is asserted, and with the AND
operator, if the setpoint should not be operated while the critical trigger is not
asserted.
Using Numeric Triggers
For numeric (analog) triggers, a setpoint allows you to specify two thresholds
for each trigger to provide hysteresis (dead band) for setpoint operations.
The Operate Limit defines the operating threshold, and the second Release
Limit defines the release threshold for the trigger. The trigger thresholds are
specified in primary units.
If you do not want to use hysteresis for the trigger, set the Release Limit to
the same as the Operate Limit.
Using Binary Triggers
Binary (digital) triggers, like digital inputs, relays, or internal static and pulsed
events, are tested for ON (closed/set) or OFF (open/cleared) status.
The binary events are divided into two types: static events and pulsed
events. Static events are level-sensitive events. A static event is asserted all
the time while the corresponding condition exists. Examples are digital
inputs, relays and event flags.
Pulsed events are edge-sensitive events with auto-reset. A pulsed event is
generated for a trigger only once when a positive transition edge is detected
on the trigger input. The examples of pulsed events are pulse inputs
(transition pulses on the digital inputs), internal pulsed events (energy pulses
and time interval pulses), and events generated by the interval timers. The
logical controller automatically clears pulsed events at the end of each scan,
so that triggers that used pulsed events are prevented from being triggered
by the same event once again.
Using Event Flags
The PM172EH provides 8 common binary flags, called event flags, which
can be individually set, cleared and tested through setpoints and via
communications.
Event flags can be used in different applications, for example, to transfer
events between setpoints in order to expand a logical expression or a list of
actions that have to be done for a specific event, or to externally trigger
setpoint actions from the SCADA system or from a PLC through
communications.
Using Interval Timers
The PM172E and PM172EH provide two interval timers that are commonly
used for periodic recording of interval data at the time of the fault or in the
presence of other events detected by a setpoint. The timers can be
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