Modicon PLC Analog scaling

How to scale analog value in Modicon Quantum PLC Programe
which block i should use?

Thanks
Sandy

I don't believe there is a standard pre-defined function block for this. You have to roll your own using four function math and hte folowing principle:

For any unit conversion on any PLC you can use four function math with the following, which
asumes integer math:

DataOffset = Data in input register at 4 mA (or zero analog signal of whatever range - for example 0 VDC on a 0-10 VDC transmitter)

DataSPan = Data at 20 mA - Data @ 4 mA

FACTOR = arbitrary factor (multiple of 10) needed to get proper resolution and accuracy

EU = Engineering Units x FACTOR

EUOffset = Engineering Units @ 4 mA x FACTOR

EUSpan = (Engineering Units @ 20 mA - Engineering Units @ 4 mA) x FACTOR

DATA = Actual data reading in input register

EU = ((EUSpan x (DATA - DataOffset))/DataSpan) + EUOffset
ProcessValue = EU / FACTOR

For Example, 0-60 psig from 4-20 mA with resolution of 0.1 psig:
FACTOR = 10
Data @ 4 mA = 6240
Data @ 20 mA = 31208
DataOffset = 6240
DataSpan = 31208 - 6240 = 24968
EUOffset = 0 x 10 = 0
EUSpan = (60 - 0) x 10 = 600
DATA = 18975
EU = ((600 x (18975 - 6240)) / 24968) + 0 = 306
Process Value = 306 / 10 = 30.6 psig

Remeber there are several different languages available for Modicon Quantum.

Modicon 984LL does not have a predefined analog scaling function. Modicon Concept and Unity both have EFBs (elementary function blocks) for scaling. These blocks can be used directly in LD, List, and FB programming and called in ST. Look at SCALING.

Modicon 984 Ladder has a block called the PCFL (Process Control Function Library) which has quite a few functions including an Analog Input function which is a scaling function. It is available in 685E,785E and Quantum processors.

Modicon Analog Scaling Screenshot (PCFL A-IN)

Attached is a Word doc with a screenshot of the network we typically use for analog scaling.

The PCFL A-IN works just fine as long as your analog device gives you linear feedback. If necessary, you can use the PCFL EQN function for non-linear equations.

-Trevor

Thanks

Thanks
Sandeep