AMPLIFICATION CIRCUIT OF EDDY CURRENT SENSOR

PURPOSE:To simplify the configuration and to reduce the cost without requiring phase adjustment even if the material of a metal workpiece to be inspected changes by converting the output waveform of an input amplifier to a rectangular waveform using a comparator and then setting the phase equally to that of the input to a synchronous rectification circuit and then feeding it to a gate. CONSTITUTION:An output waveform A of an input amplifier 5 for amplifying the output of an eddy current sensor 1 is converted into a rectangular wave output waveform B which is synchronized with the waveform A by a comparator 11 and then is supplied to the gate of a synchronous rectification circuit 7. Therefore, an output waveform C of the circuit 7 is not related to the phase difference between the voltage between output terminals of the sensor 1 and a high-frequency voltage supplied from a high-frequency oscillator 3 and hence constantly becomes a complete all-wave rectification waveform. thus eliminating the need for the phase circuit of the amplification circuit. simplifying the configuration. and reducing the manufacturing cost.