Experimental Physics and
Industrial Control System

Benjamin Franksen <[email protected]> · Wed, 10 Dec 1997 17:32:15 +0100

Some additional discussion.

Currently the adjustment conversion (using ASLO & AOFF) is intermixed
with the linear conversion (using ESLO & ROFF), as described in the
record reference manual, eg for aiRecord:

>     1. val = RVAL + ROFF
>
>     2. val = val * ASLO + AOFF
>
>If the conversion algorithm is LINEAR, the raw value is converted via the >equation: 
>
>     3. VAL = val * ESLO + EGUL

If ROFF is not zero I find it difficult to guess what the result will
be.

IMO it is more useful to separate these steps, i.e. first do linear
conversion

	val = (RVAL + ROFF) * ESLO + EGUL

and then do adjustment

	VAL = val * ASLO + AOFF

(Similar, ie the other way around, with ao record). This means that
ASLO/AOFF adjustment operates on engeneering unit values and _not_ on
raw values, which is IMO the only thing that makes sense: The raw values
should be hidden behind record and device support and not concern the
application db designer (ASLO & AOFF are DCT settable).

Anyway, there is a problem: This changes semantics. Applications that
use a device support that sets ROFF (to sth. other than zero) and also
use ASLO/AOFF themselves are no longer working correctly with the new
version. Is this acceptable?

	Ben

-- 
The Notorious Neb Nesknarf
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System