(1) The compressor capacity is too small, which leads to the failure of the pressure reducing valve, resulting in the instability of the air source pressure;

(2) The regulator is unstable and the time constant of the control system is inappropriate, resulting in unstable signal pressure;

(3) The friction resistance of the valve rod in motion is very large, and the blocking phenomenon occurs in the contact process;

(4) The ball valve of the amplifier in the positioner is not tightly closed due to dirt wear, and the output oscillation will occur when the air consumption increases especially