Wonderware Deadband

[Ones_Zeros]

Hello
I have alarms that hover around the
setpoint to alarm into our control room.

To keep from having dozens of alarms. I read
we’re the deadband can be configured to assist
with this.

Can someone help explain how the deadband works?
For example if I have a setpoint of 800 and the value
goes up to 800 and alarms in, but drops down to 799.
Resets and goes back to alarm state.

If I set a deadband of 2. What would this do?
Would the tag value have to drop down to 798 to reset/clear?
And would the alarm still alarm in at 800 or does the deadband
affect to top end and the low end of the alarm setpoint?

Just trying to get a good understanding of how the deadband works and how it affects the alarm.

Thanks for helping

 

[parky]

Dead band normally means it will change state when + or - the dead band around the set point i.e. will not trigger until SP + Dead band and reset when SP - Dead band. so in your case the alarm would trigger at >802 & reset at <798 But then again it is Wonderware lol.

 

[danw]

A high alarm with a SP of 800 and hysteresis of 5 eng units would trip at 800, and reset when the PV drops to 795.

A low alarm with a SP of 700 and hysteresis of 5 eng units would trip at 700 and reset when the PV rise to 705.

There are oddball devices that do not use engineering units, but use something like percentage of input span, but I doubt Wonderware uses such. If it's not engineering units, it's immediately obvious when the alarm does not trip at the SP or reset at the correct calculated hysteresis point.