Experimental Physics and
Industrial Control System

"Lawrence T. Hoff" <[email protected]> · Sat, 18 Dec 2004 09:56:01 -0500

	In my application, I have a dozen "stripping foils", only 
one of which can be in use at a time. Each foil degrades with use
(related to aggregate number of particles stripped). I plan to
associated a "goodness" (or "badness") factor with each foil 
(something like a battery capacity indicator in a cell phone).
Let's assume this means a dozen analog records of some sort,
one for each foil.

	Ideally, I will provide a facility where a user can say:
"insert the best foil", which will find the foil with the highest
"goodness factor", and substitute that foil for the current one.

	To do this, I need to find the index of the foil with the
highest "goodness factor", and pass that index to the foil drive 
mechanism.

	I will probably use some sort of subroutine record to
achieve this. However, as a mental exercise, I tried to think
of how to do this with "standard" EPICS records. I could
not come up with what I thought was a "clean" solution!
Maybe someone can offer a suggestion about what I might be
missing?

	I.e. I realize that I can find the highest "goodness
factor" via a SEL record. As far as I know, that can provide
the highest value, but not which input that value came form.

	I also realize that I can use CALC records, and can
even use both the "goodness factors", and the SEL record output
as inputs to the CALC record. However, I cannot think of a 
CALC expression to compute the index, within the constraints
of the CALC field length limit. I.e. if the raw values are
in fields A-K, and the highest value (from the SEL record)
is in L, the obvious expression is:

"K==L?10:J==L?9:I==L?8:H==L?7:G==L?6:F==L?5:E==L?4:D==L?3:C==L?2:B==L?1:
0"

which is too long (AFAIK).

	I could break up the calculation into several CALC
records, or use a SEQ record to re-use a CALC record with
different formulas, but it seems to me that once the use of 
records exceeds some level of complexity, a subroutine record 
is called for.

Suggestions?

-- Larry

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System