PID adjustment problem
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I recently adjusted a double valve that adjusts the liquid level to adjust the return and outlet. The PID adjustment caused the liquid level to fluctuate up and down. The range of 20 to 2000 is basically OK. However, the two valves showed periodic switching. The outlet valve fluctuated periodically between 1 and 6 degrees. The same phenomenon happened to the return valve. The two are inversely proportional. I don’t know why. How should I adjust it? Please help!
Valve control in industrial production all has hysteresis, which is allowed as long as it is within a small error.
Take the picture above to see what is happening and describe the problem clearly. Generally speaking, there may be a problem with the PID setting or the valve installation distance.
One PID is not so easy to adjust because there is too much interference. It is better to make two PIDs, but the PV is one. But this is not the best way.