mylespetro
Member
Hey guys,
After spending most of a day Googling looking for the answer, I finally decided to make a thread and ask the experts.
I'm trying to implement a cascade PID control loop (level of a tank controlling flow out of the tank) in RSLogix Micro for a Micrologix 1100, but I have very little idea how the instructions work. I mainly work in the Studio 5000 environment and the PID instruction is a little more straight-forward to me there.
I've read up on how the analog values need to be integers in the 0-16383 range, so I've scaled the raw data coming from the level and flow transmitters (6241-31207) to 0-16383 and stored them in separate integer files, N10:0 and N11:0 respectively. I then created two PID instructions, giving them the PID files PD9:0 and PD9:1. I have the PV of the master PID set to the scaled level transmitter value (N10:0), and I tried setting the CV to PD9:1.SPS, but that gives me an error. I'm kind of operating under the assumption that CV is the output, and I thought that the .SPS bit would take that output, but it didn't. Long story short, I'm not sure my syntax/approach to the PID instruction is correct, and I can't figure out how to send the output of the master to the setpoint of the slave. Any help or direction would be great.
After spending most of a day Googling looking for the answer, I finally decided to make a thread and ask the experts.
I'm trying to implement a cascade PID control loop (level of a tank controlling flow out of the tank) in RSLogix Micro for a Micrologix 1100, but I have very little idea how the instructions work. I mainly work in the Studio 5000 environment and the PID instruction is a little more straight-forward to me there.
I've read up on how the analog values need to be integers in the 0-16383 range, so I've scaled the raw data coming from the level and flow transmitters (6241-31207) to 0-16383 and stored them in separate integer files, N10:0 and N11:0 respectively. I then created two PID instructions, giving them the PID files PD9:0 and PD9:1. I have the PV of the master PID set to the scaled level transmitter value (N10:0), and I tried setting the CV to PD9:1.SPS, but that gives me an error. I'm kind of operating under the assumption that CV is the output, and I thought that the .SPS bit would take that output, but it didn't. Long story short, I'm not sure my syntax/approach to the PID instruction is correct, and I can't figure out how to send the output of the master to the setpoint of the slave. Any help or direction would be great.