Development Of High-Precision Continuous Scanning Inductance Transducer

Inductive transducer, compared to the other micro displacement measurement devices such as capacitance sensor and grating sensor, has advantages of high sensitivity, good repeatability and relatively stable performance. Therefore, it is used widely in the roundness measuring meter systems for ultra-precision processing and measurement. In recent years, with the measurement accuracy requirement on rotating parts being higher and higher in the area of cylindricity measuring, inductive transducer's measurement precision has attracted more and more universal attention. Its development has become a main limit factor of the roundness measuring instrument. In order to raise the measuring accuracy of the inductance sensor system further, we need make the performance improvement from both the mechanical structure of the measuring head and measuring circuit. In allusion to the problem such as low sensitivity and the serious nonlinear problems, this topic did some related design and improvement on the basis of the former sensor system, made the comparative experiments and did the verification. In this paper the main work accomplished are:Firstly, according to Biot-Savart Law of electromagnetic field, the characteristics of the magnetic field and the sensitivity of the coil structure have been analyzed from the structure model of solenoid coil; And from the point view of magnetoelectricity conversion in measurement circuit, the sensitivity improvement has been analyzed. In order to propose effective measures to raise the sensitivity of system, some detailed improvement designs in the coil structure itself and the measurement circuit have been made, such as the material selection of coil and magnetic cores, size parameters optimization, voltage and frequency selection of excitation signal source and the application of switch range module.Secondly, through a large number of experiments of the original system, nonlinear problems have been found and analyzed. This article analyzes its effect factors both in mechanical structure and the measurement circuit, gives the introduction and comparison of the common nonlinearity correction methods, puts forward the nonlinear compensation scheme and programs in the system software. Therefore the nonlinearity correction of the system has been realized.Thirdly, this paper contraposes the localization problem met in the roundness measurement, especially designs the sampling trigger control module in the measuring system which realizes the time control of sampled data, ensures the repeatability of collecting data and makes the roundness assess more reliable. Finally, the comparative experiments of the inductance sensor system have been done and verified the improvements'effectiveness to its performance in this subject. Experimental results show that the system has increased sensitivity two fold, nonlinear error has decreased from original 3.4% to 0.41%. The system's stability and repeatability have also been improved.