Peter Nachtwey
Member
Don't go past go. Do not collect $200 until you get the P gain working.
If it doesn't then move the level sensor.
This should make little difference if the water flows freely. You mentioned mud. That may not flow freely. The question is does the fluid flow freely?Gentlemen,
Once again, thanks for all your input. I'm on site and working on a couple of other things so I haven't got a chance to get back to my PID tuning. I hope to resume tomorrow.
I have being unable to find out the pump capacity or channel volume yet however I have made one mistake. I mentioned the LT was located 500m from the pump. This in fact is only 88Metres from Pump.
If it doesn't then move the level sensor.
Either one will do.I have a couple more questions/observations you may be able to assist my understanding.
The PID instruction in RLL in Logix offers 2 Equations, Dependent or Independent. At present it is set at Independent. Is this correct?
Yes, if PV>SP the result is positive which will speed up the pump.The control action is PV-SP. Is this correct?
Should be more than fast enough.The PID is fired off a 500ms timer. The loop update time of the PID instrction is set to 500ms too. DO these have to match? Is every 500mS sufficent? Insufficient?
Yes, the flow is not proportional to the control signal. You system is non-linear but don't worry about that until you get the P working.The VSDs mimium speed and Fieldbus minimum speed is clamped at 25Hz. I'm told if the pump is running any lower than this the pump is doing no work. Surely this is going to have an effect on my PID?
Why, not unless the pump has twice the capacity of the in flow. Ideally the pump should have just enough capacity to match the maximum inflow.Should I set my CV High Limit to 50%??
Why do that? If the bias is set to 50% the will be a 50% control output when there is no error. That isn't right.ydTech, you mentioned fixing the bias to 50%. Is this the output bias parameter in the PID instruction?