+1 to +5 VDC Input Scaling on a -10 to +10 VDC AI Card

I have a SMC PAV Module on the field which supplies air pressure of 38.4PSI as required to machine operation.

The output rating of PAV is 0.7 to 70 PSI. Now, I’m using a Beckhoff EL4034 AO module to control the PAV. The AO is -10 to +10VDC and input of PAV is rated at 0 to 10VDC. It works fine as this is a simple scaling.

This PAV also has a feedback (input to PLC) cable which I connected to a Beckhoff EL3102 AI. This AI is -10 to +10VDC rated. And the feedback of PAV is (strangely) rated at +1 to +5 VDC. I can’t properly do the scaling of this in my codes.

In short, I want to monitor running air pressure in PSI in my machine.

Where components are:

AI CARD (EL3102): -10 to +10VDC
SMC PAV (ITV2030-31N2L4): +1 to +5 VDC
SMC PSI Rating: 0.7 to 70 PSI.

How do I do the scaling in my code to monitor the exact air pressure?

Use a scale block to scale your raw counts to volts then a scale block to scale volts to pascals.

OR, use your high school maths to calculate the raw count values for 1V and for 5V and scale accordingly.

What is the resolution of the PLC AI card? Look for something like 12 14 16 bits in the manual. As you will use only half the range you also waste half the resolution meaning every change in read AI value corresponds to a higher change in PSI than with an AI card more matching the input range.

spaderkung said:

What is the resolution of the PLC AI card? Look for something like 12 14 16 bits in the manual. As you will use only half the range you also waste half the resolution meaning every change in read AI value corresponds to a higher change in PSI than with an AI card more matching the input range.

Click to expand...

It's a 16 bits resolution AI Card.