Experimental Physics and
Industrial Control System

Donny Domagoj Cosic via Tech-talk <tech-talk at aps.anl.gov> · Mon, 29 Mar 2021 14:32:39 +0200

Hi Marty and Mark,

Thank you for your quick response.

What Marty suggested makes sense. If the record is processes in INPA,

than of course INPB reads the same value from the Charge record. Thank

you for pointing that out.

However, when I corrected this error as you suggested, the result was

still always 0. Changing the order of NPP before PP should have solved

this problem but it didnt.

Using Marks suggestion of setting B to A after the calculation

("B-A;B:=A") works as expected and yields the correct result. This

solves my problem, but I still dont understand why Marty's suggestion

didnt work.

Thank you,

---
Donny Domagoj Cosic
 Institut Ruđer Bošković, Bijenička cesta 54, 10000 Zagreb, Croatia

Dana 29.03.2021 13:48, Smith, Martin via Tech-talk je napisao(la):

Hi Donny,

 Because the Charge record is Passive scan and is being processed
(presumably) only by
 the calc record what you are saying makes sense. the calc record
processes the charge
 record first for link A using a PP link causing it to get a new
value, then it gets that new

 value again using link B without processing (NPP) the charge record.

 I think what you really want is this:

 record(calc, "$(KEIT):CalcCurrent")
 {
 field(SCAN, "1 second")
 field(INPA, "$(KEIT):Charge NPP") # Get the current value of Charge

 field(INPB, "$(KEIT):Charge PP") # Process charge record then get the
new value
 field(CALC, "B-A") # You may need to change this to A-B if you want a
positive value assuming the charge is always increasing
 }

 You need to get the current value first then process the record to
get the new value.

 Marty

-------------------------

FROM: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Donny
Domagoj Cosic via Tech-talk <tech-talk at aps.anl.gov>
 SENT: Monday, March 29, 2021 6:35 AM
 TO: Tech-talk <tech-talk at aps.anl.gov>
 SUBJECT: Rate of change calculation

Hello,

 I am trying to calculate the rate of change of a record using a calc
 record as follows:

 record(ai, "$(KEIT):Charge")
 {
 field(DESC, "Measure Charge")
 field(DTYP, "steam")
 field("@devKeithley6514.proto measureCharge() $(PORT)")
 field(SCAN, "Passive")
 }

 record(calc, "$(KEIT):CalcCurrent")
 {
 field(SCAN, "1 second")
 field(INPA, "$(KEIT):Charge PP")
 field(INPB, "$(KEIT):Charge NPP")
 field(CALC, "B-A")
 }

 The calc record always returns 0. If I change the calc to B+A, to
check
 what is going on, I always get double the charge. It seems like the
PP
 and NPP are both returning the same value even though the actual
charge
 is changing. Any ideas on why this would be happening or suggestions
 would be greatly appreciated.

 Thank you in advance,
 Donny

 --
 Donny Domagoj Cosic
 Institut Ruđer Bošković, Bijenička cesta 54, 10000 Zagreb,
Croatia

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System