Today is...
Tuesday, June 19, 2018
Welcome to, the global online
community of automation professionals.
Featured Video...
Featured Video
Watch an animation of a conveyor stacking operation demonstrating the use of a move on a gear command.
Our Advertisers
Help keep our servers running...
Patronize our advertisers!
Visit our Post Archive
Scaling an Analog Input
how do i scale an analog input? Please explain everything in steps with some examples.

i want to scale an analog input. i am using delta SV2 PLC with expansion analog module which is having an ADC of 12 bit.
can anyone please explain me everything in step by step procedure.

Analog modules typically come set up for 4 - 20 mA, but your instruments are set up to measure a range.

For example, you have a temperature transmitter set for 50 to 300F

At 50F the output will be 4 mA at 300F the output will be 20mA. So you need to scale the analog input so the input is in degrees F.

Somewhere in the PLC configuration you will find a menu like "System Configuration."

Clicking on that should call up a display similar to the module layout. Try clicking on the image of the analog module. (I'm using Click software here which I think may be in the same family.)

Clicking on mine it opens up the modules
Input CH1, input CH2, etc.

Input Range Scale Range
Max 20 mA 100
Min 4 mA 0

The default scale is 0.0 to 100.0. 0 - 100% or it might be something else. It's just the starting point, most people display in engineering units these days.

So I would change the scale range to read 50.0 to 300.0. Now the numbers are in engineering units F.

Usually somewhere on this screen you will be able to set up how many decimal places to display. Try to pick scale ranges that are rounded off. This will become obvious when you start displaying the process variable on bar graphs or trend charts.

So to reiterate all you are doing is matching the scale of the PLC to match the scale on the transmitter, give it a go.