Experimental Physics and
Industrial Control System

"Zimoch Dirk \(PSI\) via Tech-talk" <tech-talk at aps.anl.gov> · Tue, 26 Jan 2021 10:33:18 +0000

On Mon, 2021-01-25 at 12:16 -0800, Randall Cayford via Tech-talk wrote:
> I have a device which returns a value and a string indicating the units of the value.  I’ll get inputs like 0.3nA or
> 3.4mA, etc.  Since I want to report the value in a consistent unit, I want to convert the unit string to a scale
> factor (nA=1, uA=1000, mA=10000) and then use a calc record to scale the value.   CALC records seem to only take
> numbers as input and I don’t see any other appropriate record type.
> 
> In programming I would use a case statement or if-elseif constructs.  How do I do this with EPICS record processing?
> 
> Randall
> LBNL
> 

When using StreamDevice, you can use regular expression preprocessing to modify the unit prefixes.
Assuming the possible units are nA, uA, and mA (not A) and you want everything in nA, you can convert the unit prefix
letters to exponential scaling factors like this:

    in "%#/u/e3n/%#/m/e6n/%fnA";

Then "uA" becomes "3enA" and "mA" becomes "e6nA". Your example "3.4mA" becomes "3.4e6nA" before "%fnA" reads it.

Dirk

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System