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Goals and Symptoms
How to reverse the logic of a Digital value in PLSCADA?
Causes and Fixes
To reverse the logic of a digital value in PL SCADA, use a NOT in front of the Variable Tag in the expression box where the tag name is used.
A NOT can be used to reverse the logic for an Alarm, specifically, when a digital device has a Normally On state (1), and is actually in alarm only when the value is Zero (the OFF state).
The screen capture below shows an example of using NOT in the Variable Tag A field of a Digital Alarm:
The following capture is an example of a Genie utilizing reversed logic. In this case, the graphic symbol will be hidden as long as the substituted variable tag is equal to one.