Design Of Excitation Supply For Elastic Permeability Measurement

Soft magnetic material is an indispensable functional material in the national economic development. The performance parameters of soft magnetic material reflect the manufacturing technology and processing technology of material production procedure directly and also is the key technical parameters for its applications, particularly with the wide application of each type of sensor, demand of soft magnetic material increases continually and the makes greater demands on measuring method and measurement accuracy of these parameters. Elastic permeability is one of the most important parameter of the softmagnetic material, but the results of the parameter measurement features large deviation and low accuracy by using genaral signal source as excitation supply in the measurement. The operation of traditional measurement method is trivial with low efficiency, which could not meet with the demand of the modern enterprises. Therefore, it is necessary to design specialized excitation supply and achieve automatic measurement.The study of researching, production and applications of the soft magnetic material is made in detail, and in accordance with the verification regulation promulgated by National Institute of Metrology PR. China (NIM), this paper analyses current several measurement methods in deep, focus on the effect of excitation supply and the sample preparation on the measuring result, and then conducted the confirmatory test. The works for the excitation supply design is as following:(1) The paper sets up the measuring equipment based on three voltage mothod after summarize and analyse these method recommended by NIM. Each index of excitation supply was formulated according to national standard and the actual need. (2) In order to achieve a high-quality, the direct digital frequency synthesis (DDS) technique is adopted, and for the sake of decreasing spurs of the output signal, phase jitter and ROM compression method be used to improve the DDS structure. (3) Upon the foundation of theory analysis, this paper determine the parameters of the DDS on the basis of the index of the excitation supply, and implement the new DDS structure based on FPGA; The low pass filter which cut-off frequency could be adjusted to the output frequency was done to the output signal; Two DACs cascadeing and resistance attenuation network were combined together as voltage amplitude control circuit; An OCL power amplifier circuit as output stage to improve the drive capability. (4) PC control system was designed based on Lab VIEW development platform, and automatic measurement will be realized easily when the acquisition system be added in future.At last, It measure the reference sample 1J50 and 1J79 using the excitation supply many times and at distinct frequency. The results showed that the stability and accuracy satisfied requirement of national standard, compared with using a general signal source as excitation supply, the stability is greatly improved.