What is the unstable air pressure of SMC electric proportional valve (the thrust sensor is controlled by amplifier and PLC) and how to solve it?

There are many reasons for instability. The range selection of 1 is incorrect. For example, you often need to output the air pressure of 1-2 kg, but the field environment is poor, so choosing the range of 5 kg will cause interference. At the same time, the proportional valve housing 3 SMC with no filter circuit at the access end is not grounded, which is easy to burn out and be disturbed, so the signal floats, resulting in unstable air pressure output. It is recommended to choose the proportional valve of Cosys, which is a company specializing in proportional valves. Cosys is grounded.