Designation And Implementation Of Portabe Non-Contact Resistivity Tester

Resistivity is an important parameter to measure the conductivity of materials.Whether it is the characterization of the conductivity of materials in the semiconductor industry or the detection of flaws in the aerospace industry,accurate measurement is of great significance.The traditional resistivity measurement method is mainly based on the four-probe method,but this method is destructive to the measured object.As the thin film of materials becomes thinner,non-contact non-destructive testing technology has attracted more and more attention.Therefore,based on the eddy current test theory,the sensor probe circuit is designed,and the hardware and software design of the signal acquisition,processing,storage and touch screen display modules are carried out.The portable test has a test accuracy of less than ±5%.Resistivity test prototype.The main research contents and results arc as follows:1.From the eddy current theory,the equivalent model of the probe coil is analyzed,and the detection scheme of the square resistance is established.2.According to the detection scheme,a probe circuit for detecting the sheet resistance is designed.It includes an oscillating circuit,an rms conversion circuit,and a zeroing amplifying circuit.The sheet resistance of the material to be tested can be converted into an AC voltage signal,and then converted into an readable DC voltage signal by RMS conversion and zero amplification.3.Design a set of signal processing and display circuits based on single chip microcomputer.The circuit has an automatic gain adjustment function to balance the measurement accuracy of high and low resistance;it has a function of storing and exporting historical measurement data;and a touch screen display function with good human-computer interaction.4.Developed a square resistance test prototype.After calibration,the measurement range of the prototype is 4-250Ω/□,and the measurement accuracy is ±5%.