1. The working principle of the pressure proportional regulator is that when the steam pressure of the boiler deviates from the rated control air pressure, the bellows 3 deflects the balance bar 1 to drive the scribing needle 2 to swing, changing the position of the contact head of the scribing needle on the sending potentiometer 4, thus converting the steam pressure signal into an electrical signal in proportion and outputting it. At this time, the sliding contacts of the two potentiometers are symmetrical, and the bridge is in a balanced state, that is, r 1 R4 = r 1 R4, and the potential difference v of the two sliding contacts is 0, so there is no signal output.

2. The working principle of electric proportional manipulator is that the power is reversible motor M, and its rotation and stop are controlled by pressure proportional regulator. The cam is mounted on an output shaft driven by a reversible motor. When the output shaft rotates, the cam pushes the crank arm to make the pointer slide on the feedback potentiometer to achieve the purpose of electric following. The sending potentiometer 4 of the pressure proportional regulator and the feedback potentiometer 9 of the electric proportional operator form a bridge circuit. When the steam pressure fluctuates, it can be adjusted by adjusting the damper, baffle and opening the oil return valve.