Oscillation Voltage Characteristics of Eddy-Current Displacement Sensor with Self-Oscillation Circuit.

Abstract

　Eddy-current displacement sensors (EC displacement sensor) are used in a variety of industries, such as detection of shaft vibration for power generation turbine. An EC displacement sensor is composed of a coil, a coaxial cable and impedance / output voltage (Z/V) converter. Z/V converter composed of Colpitts oscillation circuit and rectifier circuit. In addition, impedance of EC displacement sensor probe is used for a part of Colpitts oscillation circuit. If output and oscillation voltage of a self-oscillation circuit and impedance of EC displacement sensor probe are calculated, design of EC displacement sensor of a self-excitation circuit becomes facilitated. In this paper, impedance of the EC displacement sensor probe by theory of Dodd was calculated. Furthermore, oscillation voltage was calculated by simulation software. Then, measured and calculated values were consistent. As a result, design of circuits of EC displacement sensor can become easy.