Method and device for detecting displacement of valve rod movement in an electropneumatic position regulator with at least one proximity sensor

A method for detecting displacement of valve rod movement in electropneumatic position regulators, comprising the steps of:

• generating a high-frequency electromagnetic alternating field by exciting a high-frequency oscillation within an LC oscillating circuit in an inductive sensor arranged perpendicular to a direction of the valve rod movement;
• damping the high-frequency oscillation as a function of displacement of the valve rod via an electrically conductive body connected to and moved by the valve rod so that the surface of the conductive body moves toward and away from the sensor as a function of valve rod movement;
• demodulating the oscillator signal and feeding the demodulated signal to a microcomputer without amplification for evaluation of the displacement-dependent damping of the oscillation amplitude;
• measuring the temperature within the inductive sensor;
• correlating the temperature with the measured oscillation amplitude in the microcomputer;
• and determining a corrected displacement signal from the correlation in the microcomputer.