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

Subject: RE: stale data monitor
From: "Redman, Russell O." <Russell.Redman@nrc-cnrc.gc.ca>
To: "'Vladimir Sirotenko'" <sirotenko@fnal.gov>, tech-talk@aps.anl.gov
Date: Wed, 10 Sep 2003 13:58:59 -0700
One possible way would be to construct a delay line of ai records, say delay0, delay1 and delay2, and a calc record.  Set their input links
   delay0.INP = (hardware)
   delay1.INP = delay0 NPP
   delay2.INP = delay1 NPP
   calc.INPA = delay0 NPP
   calc.INPB = delay1 NPP
   calc.INPC = delay2 NPP
and their forward links
   delay0.FLNK = calc
   delay1.FLNK = delay0
   delay2.FLNK = delay1
Processing starts with delay2 which gets its new value from the current value of delay1, then causes delay1 to process.  Delay1 gets its new value from the current value of delay0, then causes delay0 to process.  Delay0 gets its new value from the hardware, then causes the calc record to process and compare the three values.  Initializing the chain might be a bit of a chore, however. 
 
If you need to do this in more than one place, this purely EPICS solution is not likely to be the best solution.  It is a bit more of a fuss to configure, but it would probably be easier in the long run to write a few lines of C code to put into a subr or gensub record. 
Cheers,

Dr. Russell O. Redman
Tel: (250) 363-6917 | Fax: (250) 363-0045
<mailto:Russell.Redman@nrc-cnrc.gc.ca>
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-----Original Message-----
From: Vladimir Sirotenko [mailto:sirotenko@fnal.gov]
Sent: Wednesday, 2003 September 10 12:24 PM
To: tech-talk@aps.anl.gov
Subject: stale data monitor

Hi,
 
Is there easy and natural way to monitor stale data from, say, ai record just using EPICS records? For example, I have to send alarm when several consecutive reading return the same value. The time interval for those consecutive reading may be rather large, of the order of minutes. If it would be shorter, I could use seq record with delays, but for several minutes interval how can I trigger its processing?
 
Thanks,
Vladimir
 

Replies:
Re: stale data monitor Bob Dalesio

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