Analysis And Design Of High-temperature Eddy Current Displacement Sensor

This paper begins with analysis and design of eddy current displacement sensor under common environment, then to high-temperature eddy current displacement sensor operating from room temperature to500℃.First, the background and state-of-art development in related field are introduced. Special attention is paid to methods to compensate for temperature effects. Brief introduction is also paid to inductive and capacitive displacement sensor.Second, a simulation transformer model to quantitatively calculate the output impedance of probe coil is built to simulate the electromagnetic coupling system between target material and sensor probe, which provides a way to analyze the effects of environmental parameters on output impedance of probe coil.Third, a kind of eddy current displacement sensor, which has the capacity to operate its function under room temperature, is designed and analyzed. The principle of frequency-constant voltage-modulated circuit is adopted as the base structure of signal processing circuit. The output properties of designed sensor is measured and optimized by experiments on the stationary calibration system.Forth, problems that would arise when eddy current displacement sensor is applied in high temperature environment are analyzed and improvements to solve these problems are provided. Another problem to accurately seperate displacement and temperature information under any given environmental parameters merely by analyzing the output impedance of sensor probe is detailed analyzed in both mathematical deduction and simulation verification. This research provides basement for the feasibility of displacement measurement by analyzing the output impedance of probe coil for eddy current testing technology.Fifth, a kind of high-temperature eddy current displacement sensor, which could operate from25℃to500℃, has been designed. The sensor probe could be adapted to high temperature by improvement of probe material and the added temperature-compensation section. The output property of sensor is measured in temperature-controlled system to verify the validation of temperature compensation strategy. Besides, a novel temperature-compensation method based on AC-DC coupling strategy is briefly introduced and then follows its advantages and disadvantages.