PID motor control surging/overshooting

[TJA]

I can't get the PID motor control to settle down, when starting the motors.
It surges past the desired vacuum level and then back below it.
This is so extreme, that I need to switch it immediately back to manual in order to not overshoot the 40" DM limit.

When I got the bench together, I could and still can use the automatic PID control when the cfm is high.
The problem is, that starting the measurement @0.100" the flow is very low and the PID control doesn't settle down,
but keeps hunting the set value.

The bench is the 8 motor 3-phase version in Europe.
It now has the soft start enabled and that might be causing the behavior.
I just can't remember, how to disable the soft/delayed motor spooling ?

All the parts are from the PTS store: SSRs, DM, PID motor control.

I've tried to start the motors slowly and gradually, but that did not do the trick.
I also tried to set the pressure manually an then flipping the switch to auto, but that failed also.

[Brucepts]

Sent a private message

[TJA]

Thank you Bruce.