Return to normal (RTN) alarm setting on AI point not functioning as expected

Issue

When using Conversion Coefficient slope m = 1.0, the return to normal (RTN) Alarm Limit on an AI point appears to have a built-in offset.

Product Line

TAC I/NET

Environment

I/NET Seven - Analog Inputs (AI), all revisions.

Cause

There is a built-in hysteresis of 3 counts on the return-to-normal settings for both the low and high limit setting of an analog input (AI) point.  When using a conversion coefficient slope (M) of 1, this provides a 1:1 scale between counts and engineering units which could provide undesired results.  So this built-in hysteresis needs to be considered when using a slope (M) of one or higher on analog input alarm points.   

Resolution

Consider using a conversion coefficient slope (M) of 0.1.  Alternatively if this is not possible, creating an internal AI point (using a m = 0.1) or a DA and applying a calculation to reflect the points value or alarm state as required as a workaround.