Greetings All,
I have a very simple process where DV takes in level information from a tank radar and then controls a motor/pump speed that pumps product into that tank (the output is handled by a different motor/pump that runs at a constant speed).
Normally, we set everything up in manual mode, getting the motor speed right, getting the tank level up to nearly correct, and then we switch over to automatic, giving DV control of the motor.
When that happens, even if the tank level is slightly below target, the motor immediately slows way down, which then causes the tank level to drop. DV then speeds it way up, causing the tank level to be too high, then it slows way down, etc. It takes about 10 minutes for it to finally settle out. After that, it's fine.
DV is managing the motor VFD via an analog out signal to a voltage input on an Allen Bradley Powerflex 70.
The set up is a challenge, because the tank is actually quite small, so the difference between level too low and too high is only an inch or so.
It seems like the process isn't even looking at the radar signal upon switchover, it's just immediately sending the VFD signal low.
Hopefully this is enough information to describe the problem, and someone has some kind words of advice for me.
Thank you so much