Quantity Based Channel scaling

[Brok]

I need to change the scale of a channel using the function ChnLinScale(ChnScaleInputChannel, ChnScaleOutputChannel, ChnScaleFactor, ChnScaleOffset).

The ChnScaleInputChannel has an arbitrary unit (i.e., A, mA, kPa).

The parameters ChnScaleFactor and ChnScaleOffset must be calculated from these equations.

ChnScaleFactor = (PhysicalRngUpper - PhysicalRngLower) / (MeasuredRngUpper - MeasuredRngLower)
ChnScaleOffset =  - ChnScaleFactor * MeasuredRngLower + PhysicalRngLower

The parameters  PhysicalRng and MeasuredRng can also have arbitrary unit.

MeasuredRng has the same physical quantity as ChnScaleInputChannel (current, voltage, etc.), but usually does not have the same unit.

In short, sometimes I need to convert the "mA" range to "kPa", other times "A" to "MPa". Any combination is possible.

I tried this calculation script but it doesn´t seem to work properly - see attachment "Calculation failed.png". With "Quantity-based" turned off the script works fine.

'Calculation Script Body
'------------------------------------------------------------------------------------
If Not This.QuantityBased Then
    ChnScaleFactor.Value = (PhysicalRngUpper.Value - PhysicalRngLower.Value) / (MeasuredRngUpper.Value - MeasuredRngLower.Value)
    ChnScaleOffset.Value = -ChnScaleFactor.Value * MeasuredRngLower.Value + PhysicalRngLower.Value
    Call  ChnLinScale(ChnScaleInputChannel, ChnScaleOutputChannel, ChnScaleFactor.Value, ChnScaleOffset.Value)
Else
    
    Call Calculate(" ChnScaleFactor = (PhysicalRngUpper - PhysicalRngLower) /(MeasuredRngUpper- MeasuredRngLower)",CurrSymbols,CurrValues,"")
    Call Calculate(" ChnScaleOffset = -ChnScaleFactor * MeasuredRngLower + PhysicalRngLower",CurrSymbols,CurrValues,"")
    Call ChnLinScale(ChnScaleInputChannel, ChnScaleOutputChannel, ChnScaleFactor, ChnScaleOffset)
End If

I'd like to avoid adding new units to the database, I probably just need to get Diadem to correctly calculate ChnScaleFactor and ChnScaleOffset with respect to the input channel unit and input/output range unit.

Any help is appreciated.

John

[AndreasK]

Did you have a look at the build in conversion mechanisms?

Normally this should help on your job.

Try it in the Data portal when pressing the ... button behind the unit of your channel and use teachin to see the sript.

ChnConvertUnit("[2]/Noise_1", "[2]/Noise_1", "kPa")

[Brok]

Hello

Thanks for the hint.

I finally used similar approach and it seems to be working.

I spent some time trying to make Diadem to calculate it all by itself. But there were many problems.

Especially with unregistered units. I wanted to avoid having to constantly register new units combinations (e.g. kPa/m, kPa/mA etc.) 

Also the function ChnLinScale probably takes parameters ChnScaleFactor and ChnScaleOffset as dimensionless.

So I finally turn off Quantity-based option and added few lines of code and this is the result. 

'-------------------------------------------------------------------------------
'Calculation Script Body
'-------------------------------------------------------------------------------
 
 Call MeasuredRngLower.Convert(ChnScaleInputChannel.UnitSymbol)
 Call MeasuredRngUpper.Convert(ChnScaleInputChannel.UnitSymbol)

 ChnScaleFactor.Value = (PhysicalRngUpper.Value - PhysicalRngLower.Value) / (MeasuredRngUpper.Value - MeasuredRngLower.Value)
 ChnScaleOffset.Value = -ChnScaleFactor.Value * MeasuredRngLower.Value + PhysicalRngLower.Value
 Call  ChnLinScale(ChnScaleInputChannel, ChnScaleOutputChannel, ChnScaleFactor.Value, ChnScaleOffset.Value)

'-------------------------------------------------------------------------------
' post-processing
'-------------------------------------------------------------------------------
 If PhysicalRngLower.UnitSymbol <> vbNullString Then
        ChnScaleOutputChannel.UnitSymbol = PhysicalRngLower.UnitSymbol
 ElseIf PhysicalRngUpper.UnitSymbol <> vbNullString Then
        ChnScaleOutputChannel.UnitSymbol = PhysicalRngUpper.UnitSymbol
 End If

By the way, when I was fiddling with quantity-based calculation I came across a few oddities.

For example the second part of this code returns wrong unit. (at least in Diadem 2023 Q2)

Dim sFormula, aSymbol(6), aMyValueUnit(6)

CalcQuantityBased = TRUE

aSymbol(1) = "I1"
aSymbol(2) = "I2"
aSymbol(3) = "O1"
aSymbol(4) = "O2"
aSymbol(5) = "Factor"
aSymbol(6) = "Offset"
Set aMyValueUnit(1) = CreateValueWithUnit(4, "s")
Set aMyValueUnit(2) = CreateValueWithUnit(20, "s")
Set aMyValueUnit(3) = CreateValueWithUnit(-1, "m")
Set aMyValueUnit(4) = CreateValueWithUnit(10, "m")
Set aMyValueUnit(5) = CreateValueWithUnit(null, "")
Set aMyValueUnit(6) = CreateValueWithUnit(null, "")

sFormula = "Factor= (O2-O1)/(I2-I1)"
Call Calculate (sFormula, aSymbol, aMyValueUnit, "")
'Result's unit is correctly  'm/s'

sFormula = "Offset = -Factor * I1 + O1" 
Call Calculate (sFormula, aSymbol, aMyValueUnit, "")
'Throws error 'Invalid "s"(+)"m" unit conversion', because result's unit of 
-Factor * I1 is incorrectly  's'

sFormula = "Offset = (-1) * Factor * I1 + O1"
Call Calculate (sFormula, aSymbol, aMyValueUnit, "")
'Result's unit is correctly  'm'

Or this example. It is using syntax from Diadem help.

CalcQuantityBased = TRUE

Call Calculate("R1=(VU(20,""m"")-VU(4,""m""))/(VU(10,""s"")-VU(-1,""s""))",,,"")
LogFileWrite R1 & " " &  CalculateResultUnit
'Output is correct 'm/s'

T1 = CalculateResultUnit

Call Calculate("R2= -1* R1 * VU(-1,""s"") ",,,"")
LogFileWrite R2 & " " &  CalculateResultUnit
'Output is incorrect 's'

Call Calculate("R2= -1* VU(R1,T1) * VU(-1,""s"") ",,,"")
LogFileWrite R2 & " " &  CalculateResultUnit
'This doesn't work at all

 Maybe, I can't use correct methods, syntax or whatever. 

John