17 years ago
I am working on a project where I am not sure whether I should use PID
control or not. Any suggestions would be greatly appreciated.
I have a hopper on load cells. There is an auger at the bottom that is
mechanically connected to a PD pump. I need to control mass flow. I have
specified a weigh transmitter that will give me both current total weight
and rate of change (over ControlNet). The reason that I spec'd the rate of
change was that I was hoping that it would give me more accurate
information. My thought was that it would be faster to have the transmitter
do the filtering / averaging than to have the PLC do it with the total
weight information and doing a moving average.
I am having second thoughts on the need for PID control (well actually just
PI). I am trying to make this as accurate as possible and am worried about
the dead time that I will have due to the delay in waiting for "good" data.
Also, I am thinking that the response is not going to be anything like a
1st order lag with dead time and would be straigh proportional. Is the
delay in waiting for "good" data consider dead time, seeing as how it is
not related to the process?
Does this make sense? Does anyone have any experience with anything
Thanks again for any help!!