Re: looking for OSI version of epid record

[Tim Mooney <mooney@aps.anl.gov>]

LYNCH, Damien wrote:
> I am interested in the response to the following question as well (as I have
> just started using EPID this week myself).
>
>
> > Another question with regard to replacing pid by epid: Apart from teh above
> > scaling issue, have I understood it correct that if the following scenario:
> >
> >
> > a pid record controlling an ao record, the latter in OMSL=closed_loop, 
> > output OIF=incremental mode, DOL referencing pid's DM
> >
> > would be replaced by
> >
> > epid record having OUTL point to ao record's VAL, ao record in OIF=full and
> > OMSL=supervisory mode?

Yes.  This allows the epid record to control any record, to have its output
value transformed by a calc expression, etc.

> I see the EPID record producing a value that should be added to the ao
> record's VAL field, implying the ao record should have OIF=Incremntal. But
> with the EPID record putting OVAL into what's pointed to by OUTL (ie the ao
> record) I'd expect to have OMSL=supervisory in the ao record.

Hang in there and see what happens as the controlled value responds to the
new output value.  With KP!=0 and KI==KD==0, you should see ERR=VAL-CVAL, and 
OVAL=KP*ERR.  If not, do a "dbpr" on the record and send that.  There might be
some control field we're not thinking about with an unexpected value.

> The way I read the doco I thought EPID would calculate a value that would be
> put into the ao record (not added to what's already there).

That's the way it's supposed to work.

--
Tim Mooney (mooney@aps.anl.gov) (630)252-5417
Beamline Controls & Data Acquisition Group
Advanced Photon Source, Argonne National Lab.