Re: Scaling mA to A: EPICS or Phoebus?

[Michael Davidsaver via Tech-talk <tech-talk at aps.anl.gov>]

I would suggest looking into the ALSO/AOFF fields of ai/ao.

The most direct way to explain their usage is to quote the code in streamDevice:

>             if (ai->aslo != 0.0 && ai->aslo != 1.0) val *= ai->aslo;
>             val += ai->aoff;

https://github.com/paulscherrerinstitute/StreamDevice/blob/a9e0fb7beb74ed0868995934085b5c7e412ce84c/src/devaiStream.c#L38

>             if (ao->aslo != 0.0 && ao->aslo != 1.0) val *= ao->aslo;
>             ao->val = val + ao->aoff;

https://github.com/paulscherrerinstitute/StreamDevice/blob/a9e0fb7beb74ed0868995934085b5c7e412ce84c/src/devaoStream.c#L36-L37


On 6/23/23 09:19, Leblanc, Gregory via Tech-talk wrote:
> Hi folks!
>
> I'm trying to get a basic control implemented for our new Heinzinger PCU 50-300 supplies.  These supplies operate best using RS-422, and I've got EPICS talking to a Keysight 4-port USB to RS-422 adapter.  I'm going to skip over the .proto file, since it seems to be working (I'll try to get something uploaded somewhere once I finish testing).  I've got a .db file with the following two entries:
>
> record(ai, "$(P)$(R)GetCurrent") {
>      field(DESC, "Read output current")
>      field(DTYP, "stream")
>      field(INP, "@devPCU50_300.proto getCurrent $(PORT) $(A)")
>      field(EGU, "mA")
>      field(SCAN, "1 second")
>      # field(SCAN, "Passive")
>      field(PINI, "YES")
> }
>
> record(ao, "$(P)$(R)SetCurrent") {
>      field(DESC, "Write output current")
>      field(DTYP, "stream")
>      field(EGU, "mA")
>      # field(SCAN, "1 second")
>      field(SCAN, "Passive")
>      field(OUT, "@devPCU50_300.proto setCurrent(%d) $(PORT) $(A)")
>      field(PINI, "YES")
>      field(VAL, "0")
>      field(FLNK, "$(P)$(R)GetCurrent")
> }
>
> These power supplies expect commands in mA, and return results in mA, so I made my Phoebus display (bob file and screenshot attached) using mA, and it works OK.  But given that these supplies have an output current of 300A, 300,000 mA looks silly and is hard to read.  Is there a preferred method of tackling this problem?  Since there are "hints" as to the units in the records, it seems like someone has probably run into this before, but I didn't find anything when I searched.  Any advice greatly appreciated!
>       Greg
>
> --
> Gregory Leblanc
> Accelerator Engineer
> Edwards Accelerator Lab - Ohio University
> 123 University Terrace
> Athens, OH 45701 USA
> leblanc at ohio.edu
> M: (401) 52-OUAL1 or (401) 526-8251