Hello,
I'm an intern at this power plant and I'm new to PLC programming. I'm hoping to get some help from the professionals in this forum.
I ran into a problem while working on adding a PID loop that controls a heat exchanger outlet temperature for an air dryer system.
The controller include:
- Micrologix 1200
- 1762-IF4 module
- 1762-IF2OF2 module
The problem:
- I added an PID function on a separate program file with a SCP function to scale the data for PID loop. Somehow, the SCP function keeps giving ZERO output.
+ SCP setup
input: I:1.3, input min: 6241, input max: 31206
scaled min:0, scaled max: 16383, output: N7:41
- The temperature input (I:1.3) comes from IF4 card which was not "Scaled for PID" by the original programmer. T3 is in correct range.
- The PID controls an output of IF2OF2 card which connected to a proportional valve.
- There are other SCP functions used in a different program file and they are working fine, including (I:1.3) input but different scaling unit.
- I tried to use SCL but it gave ZERO output as well.
Please help!
Thank you!
I'm an intern at this power plant and I'm new to PLC programming. I'm hoping to get some help from the professionals in this forum.
I ran into a problem while working on adding a PID loop that controls a heat exchanger outlet temperature for an air dryer system.
The controller include:
- Micrologix 1200
- 1762-IF4 module
- 1762-IF2OF2 module
The problem:
- I added an PID function on a separate program file with a SCP function to scale the data for PID loop. Somehow, the SCP function keeps giving ZERO output.
+ SCP setup
input: I:1.3, input min: 6241, input max: 31206
scaled min:0, scaled max: 16383, output: N7:41
- The temperature input (I:1.3) comes from IF4 card which was not "Scaled for PID" by the original programmer. T3 is in correct range.
- The PID controls an output of IF2OF2 card which connected to a proportional valve.
- There are other SCP functions used in a different program file and they are working fine, including (I:1.3) input but different scaling unit.
- I tried to use SCL but it gave ZERO output as well.
Please help!
Thank you!