RE: Alarm Handler and $ALARMCOUNTFILTER

[<keith.baker@diamond.ac.uk>]

Thanks, Andrew.
You haven't corrected my understanding of how the $ALARMCOUNTFILTER behaves so at least I know I'm not missing some trick. I'll just have to work with it as it is, or like you say, implement an alternative in the IOC.
I was partly after confirmation that other people are happy with the way things are. Since you're using this feature a lot at ALH it clearly suits your needs.
I may risk proposing some backward compatible changes in the future, but this will take effort and it looks like I'm the only one who needs them.
Regards,
Keith.

-----Original Message-----
From: Andrew Johnson [mailto:anj@aps.anl.gov] 
Sent: 18 July 2011 17:14
To: tech-talk@aps.anl.gov
Cc: Baker, Keith (DLSLtd,RAL,DIA)
Subject: Re: Alarm Handler and $ALARMCOUNTFILTER

Hi Keith,

On 2011-07-18 keith.baker@diamond.ac.uk wrote:
> 
> My requirement is to only register an alarm if the value exceeds the
>  threshold persistently for 120 seconds.
...
> The other behaviour I've noticed is that once in alarm, the same criteria
>  is used to decide when to drop down to no alarm. i.e. if the PV value
>  drops below the threshold then it takes inputSeconds before this is
>  recognised, or inputCount drops within inputSeconds. I am just curious as
>  to whether this is behaviour that anybody wants or uses? I'd prefer to
>  drop out of the alarm state immediately.

It's likely that the behaviour implemented was required by someone at APS when 
we wrote ALH, I see it being used fairly heavily in our operational alhConfig 
files.

I would suggest that your alarm filter should probably be implemented inside 
the IOC, rather than rely on ALH to do it.  It's much easier to customize 
there anyway.

- Andrew
-- 
Optimization is the process of taking something that works and
replacing it with something that almost works, but costs less.
-- Roger Needham

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