The Software Development Of Non-linear Dielectric Measurement System

Nonlinear dielectrics are those materials, for which the conductivity and dielectric constant are function of electric field. The purpose of this paper lies in development of AC properties testing system for non-linear dielectrics based on laboratory application background. The paper focuses on researching the response characteristics of non-linear dielectrics under the excitation of AC voltage, the decomposition of the response current and the design of testing software system. The suitable software measurement system is developed.At first, a non-linear circuit model with voltage-controlled components connected in parallel is built for non-linear composite dielectrics to deduce the response current function of exciting voltage. It is presented that field-dependent equivalent conductivity and field-dependent relative dielectric constant are effective parameters to describe non-linear dielectrics under AC field. Secondly, on the basis of the brief introduction of hardware structure and whole software design for the testing system, available present signal decomposition algorithms are analyzed and compared, it is found that none of them can satisfy the subject's require. Consequently, the least squares method based on time domain nonlinear model is presented. Afterwards, the measuring software system owning combined functions of synchronous signal acquisition, signal decomposition, error correction and signal reconstruction is developed using the LabVIEW soft system. The software simulation is also made to prove the non-linear least squares algorithm is available. The software system developed by the paper and the hardware system finished by subject group are formed into a non-linear dielectric AC characteristic measurement system based on laboratory application. Finally, proving trials for the testing system and tests on SiC filled LDPE sheet samples are completed respectively. Experimental results illustrate that the testing system meets the needs of AC characteristic test for non-linear dielectrics.