Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Tue, 09 Apr 2002 14:11:37 -0500

Kay-Uwe Kasemir wrote:
> 
> At 10:20 AM 4/9/2002, Andrew Johnson wrote:
> >Doesn't the AO record already have a very similar behaviour controlled by
> >the IVOA field?  It's not quite the same, but do we really need this kind
> >of thing to be implemented twice?
> 
> IVOA happens after the clamping, it doesn't solve the problem.

If you move the DRVH and DRVL values to HIHI and LOLO instead, set HHSV
and LLSV to INVALID_ALARM and IVOA to "Don't drive" then you should get
"reject" behaviour as far as the hardware is concerned - no value outside
of the limits ever gets sent out.  However you also get the record in an
INVALID_ALARM state, which might not be quite what you want so it's not
quite the same, and you do use up a pair of alarm limits, but you don't
have to modify aoRecord.c at all to get this behaviour.

I wonder if that's an indication that the clamping is happening at the
wrong point in the processing chain, or could the IVOA field be used to
control the drive limit mode instead of adding DRLM?  Would someone ever
want both at once?  I guess that's possible, but the two concepts seem to
be pretty closely related, as they're both associated with data validation
and what to do if you get bad data.

BTW, I'm just throwing out ideas here to ensure that we think this through
properly, not violently objecting to DRLM as such.

- Andrew
-- 
Perfection is reached, not when there is no longer anything to add,
but when there is no longer anything to take away.
- Antoine de Saint-Exupery

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System