I've got a project coming up whe a proportional valve controld a hydraulic cylinder. The cylinder controld the control the window size of a slidind gate that allows varying amounts of material to discharge. The Output is a proportional valve with 12ma. closed, 12+m.a. increases flow through the valve in one direction and 12-ma. does the same in the opposite direction. The PV is a level sensor sensing the level of material in the hopper containing the material. The SP is the desired level to maintain in that hopper. The hydraulic cylinder will have no position feedback of the stroke. In the perfect world, the cylinder would open to create acertain size window for the discharge and then close at 12ma. The PV will vary based on the amount of material entering the hopper via a conveyor and being stratified to varying densities via vibration or pulsing air over the material in a water bath. Since the valve must output to a certain position, close, and settle for the next calculation and make the appropriate adjustment, the output will be going to a closed state 12ma. until it needs to make an output adjustment based on the PV. Can anyone offer some advice here. Any help or direction is greatly appreciated. A similar machine uses a rubber paddle drived at varying speeds controls the dischagre. The output is always at some level being sent to the VFD. That one is easy and easy to tune. Thaks again for any help here.