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

Subject: Re: Alarm conditions ?
From: [email protected] (Ned Arnold)
To: [email protected]
Cc: [email protected]
Date: Fri, 1 Nov 1996 08:23:01 -0600
 
> Hello,
> 
> I have to control process which has two states: RUN and STOP.
> 
> I need to implement an alarm action for the pressure value with some
> additional conditions. I have thresholds for alarms and warnings: 
> 
>      Low  severity: for Warning 
>      LoLo severity: for Alarm
>      High severity: for Warning 
>      HiHi severity: for Alarm
> 
> I want an alarm to be valid only if I am in the RUN state, pressure value
> is in the Alarm range and alarm is not inhibited. 

Implementation always depends on the number of PV's you have that require
this. If not too many, I would use a sequence record to change the HHSV, HSV,
LSV, LLSV fields to NO_ALARM when in STOP, and HIGH (or HIHI) when entering
RUN. Using the MASK mode of the sequence record, this would require one
sequence record per pressure PV.

If you have LOTS of these, a custom record type is probably more appropriate,
which has an input link from RUN/STOP to determine whether to post an alarm.

> 
> Additional requirement is: alarm is valid only after defined period of
> time (delay for validation of the alarm) 

Hmmmm, I think Janet Anderson is adding a "time delay" feature in our Alarm
Handler, but I don't know if that's what you are using. If your requirement
insists for the time delay to be at the source (the record), then an additional
"alarm" subroutine record per pressure PV could accomplish it. OR, if you
go with the custom record, you can build it in.

This application illustrates an important feature of EPICS. You can use
standard records (albeit many of them) to accomplish almost any 
unique requirement. When the requirement becomes "not so unique" and somewhat
messy, then a custom record can be developed which fulfils the requirement
elegantly.



	Ned
	


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