MEASURING DEVICE OF OPERATING STATE OF ELECTROMAGNETIC PLUNGER

PURPOSE:To dispense with a mechanical element on the occasion of measurement of the operation of an electromagnetic plunger, to enable execution of measurement even in a state wherein the plunger is fitted to another device and to obtain a high precision in measurement. CONSTITUTION:An operating current is supplied to an electromagnetic plunger 1 through a shunt resistor 31. Voltages applied to terminals 4a and 4b of the plunger 1 are inputted to a band-pass filter 32, while voltages extracted out of the opposite ends of the shunt resistor 31 are inputted to a band-pass filter 33. An output voltage of the band-pass filter 32 is divided by an output voltage of the band-pass filter 33 and the quotient is detected and converted into a pulsating voltage by a detector 35. This pulsating voltage is inputted to a low- pass filter 36 so that only a low-frequency component thereof be extracted, and this is outputted to a recorder 37 as a change of a recordable DC voltage. The relationship between the position of an inner ring 2 of the plunger 1 and time can be known from a recorded waveform 39 of this recorder 37 and the operating state of the plunger can be measured therefrom.