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<== Date ==> <== Thread ==>
Subject: scalcout and calc yielding different results
From: "Marco A. Barra Montevechi Filho via Tech-talk" <tech-talk at aps.anl.gov>
To: "tech-talk at aps.anl.gov" <tech-talk at aps.anl.gov>
Date: Tue, 12 Sep 2023 20:53:44 +0000
Hi all. I happened to bump into an interesting problem. Im using calc and scalcout records to translate a very small current measurement into a more convenient unit of measurement.

After having trouble with the software showing the wrong measurement unit, i came to the conclusion that  for some reason, although calc and scalcout are both double types, they seem to have different precision for comparisons.

I have the following example, made to get a very small amount of current in Amps and decide to either display it in pA, nA, uA, etc.:

record(ai, "CURRENT"){}

record(calc, "CALC") {

    field(INPA, "CURRENT CP")
    field(INPB, "1e-12")
    field(INPC, "1e-9")
    field(INPD, "1e-6")
    field(INPE, "1e-3")

    field(CALC, "F:=ABS(A);F<C?1:(F<D?2:(F<E?3:4))")
    field(PREC, "4")

    field(PINI, "YES")
    field(SCAN, "Passive")
}

record(scalcout, "CURRENTSCALEDUNIT"){

field(INPA, "CURRENT CP")
field(PREC, "15")
field(INPB, "1e-9")
field(BB, "pA")

field(INPC, "1e-6")
field(CC, "nA")

field(INPD, "1e-3")
field(DD, "uA")

field(INPE, "1")
field(EE, "mA")

field(CALC, "A:=ABS(A);A<B?BB:(A<C?CC:(A<D?DD:EE))")

field(OUT, "CURRENTSCALED.EGU")
field(OOPT, "Every Time")

field(PINI, "YES")
field(SCAN, "Passive")

}

record(calc, "CURRENTSCALED"){

field(INPA, "15")
field(CALC, "A")

field(PINI, "YES")
field(SCAN, "Passive")

}

However, if you caput CURRENT 9.94e-10 you will see CURRENTSCALEDUNIT.SVAL=nA and CALC.VAL=1, meaning that for the calc record, 9.94e-10<1e-09 is True but for the scalcout this is false.

Is this expected?

Thanks,

Marco

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Re: scalcout and calc yielding different results Mooney, Tim M. via Tech-talk
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