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<== Date ==> <== Thread ==>

Subject: Re: Smoothing and alarm filtering on the analog input record - a proposal
From: "Kasemir, Kay" <[email protected]>
To: "Dalesio, Leo" <[email protected]>, [email protected]
Date: Mon, 30 Mar 2009 17:11:31 -0400
Hi:

On 3/30/09 16:43 , "Dalesio, Leo" <[email protected]> wrote:
> Add the following fields
> MSEV - measured alarm severity
> MSTA - measured alarm status
> CFIL - number of scans this status must be true before it is applied
> ACNT - number of scans this status and alarm severity have been detected

Pro:
Goes into the right direction,
configuring an "alarm" is more than setting HIGH & HSV.
To avoid going in & out of alarm, you sometimes need HYST.
To avoid alarms which are too short for anybody to do
anything about them, you sometimes need delays.

> Two questions: does the count get reset every time the alarm condition
> changes? Does it need to be more intelligent?
The above implements alarm-only-when-persists-N-seconds
as for example offered by ALH, but puts it into the IOC,
which I think is good.

But more questions:
In ALH, there's also the idea of M-alarms-within-N-seconds,
as in: PV chattered in and out of alarm M times.
Never lasted N seconds, but happened M times within N seconds,
and that might be reason to alarm.
Does anybody use that?
Should it also be configurable via a new record field?

What about disabling alarms based on machine state?
That's actually very important if you want to avoid
all those nuisance alarms when things are off on purpose.
Should each record have an "alarm disable" input
to make this easier?


While somewhat inconvenient, you can of course already
implement all the delays and conditional alarming that
you want by adding calc records and/or SNL.

Thanks,
-Kay


References:
Smoothing and alarm filtering on the analog input record - a proposal Dalesio, Leo

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