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

Subject: Re: aiRecord, RVAL vs. VAL
From: "Brian McAllister" <brian@hotrats.mit.edu>
To: "Mark Rivers" <rivers@cars.uchicago.edu>
Cc: <tech-talk@aps.anl.gov>
Date: Thu, 04 Dec 2003 17:42:35 -0500
>>> On 12/4/2003 at 16:30:38 CST, Mark Rivers wrote:

  > I agree that having the RAW field be an integer is a limitation.  For
  > example, I might want to read a voltage from a digital multimeter,
  > which returns a floating point number, but then have that number
  > converted to some other units, for example pressure, by the ai record
  > conversion routine.  As it stands I think device support would have to
  > do that conversion directly, it could not write into the RVAL field and
  > ask the record to do the conversion.

One work-around for this (which is used by devAscii, for instance) is to
scale the value read from the device up in the device support so that it
can be represented as an integer while maintaining useful precision, and
then to scale it back down in the conversion to your desired units.

- brian

References:
RE: aiRecord, RVAL vs. VAL Mark Rivers

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