1746-no8i / ni8

Greetings,

I am working with a SLC 5/03 OS302 and a 1746-NO8I and a 1746-NI8.
I would like to be able to apply a 4 mA to 20 mA signal to a modulating valve at slow rate.
Is there a way that I can do this with the Output card.

I have looked at the cards manuals and just have gotten more confused.

Thanks for any and all help,

bowler

Is there a way that I can do this with the Output card.

Click to expand...

Short answer is yes.

You are going to have to tell us more. Tell us about the process it's controlling.

What is going to control the output, is this going to be done manually or automatically ( PID control ?)

Have you set-up the card yet in your program? Can you post your program ( .RSS file) zip it first.

Both cards are configured Class 3 and Scaled to PID
A transducer feeds a 4 mA to 20 mA signal to the Input card.
This goes to a SCP scaled 0 to 300 psi.
This goes to a Process Variable on a PID which goes to another SCP.
The second SCP scales 0 to 5000 and goed to the Output card.
The Output goes to the modulating valve that needs to open slowly.
I can't post the program.
Can the Output be scaled to slow down the opening of the valve?

If your output card is set for scaled for PID then sending a value of 0-5000 you will only get a max of about 9 ma output. A output card scaled for PID and 4 to 20ma out needs a value of 0-16383 to get full scaled 4 to 20ma.


As for ramping the output, this can be done by putting your PID in manual and slowly ramping the PID's output until you get the process value you want then put the PID in auto. Depending on how you set-up the PID this can be a bumpless transfer.
You also could start with a low setpoint and ramp it up slowly, using a Ramp (RMP) instruction or I prefer an addition instruction enabled periodically to add a small value to the setpoint until you reach your desired value.

I'm sure others will check in with more methods.