Inductive valve motion sensor for positioning outside the body of the

Abstract

The motion of a DISC for a check valve is tested and sensed by placing coil sensors on the check valve. The coils produce a magnetic field within the valve near the DISC such that the DISC moves through the magnetic field. The coils are connected to a sensing circuit having an LED display. The sensing circuit is also connected with a tape recorder for taping a signal output by the sensing circuit. The recorded signal by the tape recorder can be subjected to further analysis. The LED display of the sensing circuit can also be used to create a stand-alone indicator of valve actuation. An oscillator of the sensing circuit produces a sinusoidal excitation wave which is amplified and transmitted to the coils for producing the magnetic fields. The coils have approximately the same resistance and inductance such that they form a balanced bridge circuit. If the two coils are perfectly balanced, the output from the bridge circuit is zero. If the inductance of either of the coils changes, however, the output of the bridge circuit changes wherein this change is displayed by the LED display while being recorded by the tape recorder for analysis.