Method and device for three-parameter eddy current control of metal rods

The article analyzes known non-contact one-parameter and two-parameter eddy current methods and devices for controlling the geometric magnetic and electrical parameters of metal cylindrical products. The subject of the study is the development of a non-contact method and device, based on a transformer eddy current transducer, for the joint determination of three parameters of a metal cylindrical product, namely: diameter, magnetic permeability, and electrical conductivity. The aim of this work is to increase the sensitivity of three-parameter eddy current quality control of metal cylindrical products and develop a device scheme for their rejection. To achieve the aim, the following tasks were solved: to develop the theoretical foundations of a control method based on finding the frequency of the electromagnetic field of a transformer transducer with a rod under study, which corresponds to the extremum of the transformation function; to develop a device scheme and an algorithm for implementing the developed method; to conduct experimental studies in order to compare the results obtained by the developed method with control methods. Results obtained: the main mathematical expressions were found that link the measured parameters of the primary transducer signal with the information geometric, magnetic and electrical parameters of the controlled metal product; a device and an algorithm for implementing the proposed method were developed, based on finding the frequency of the field of the electromagnetic transducer with a rod, which corresponds to the extremum of its conversion function in the case of compensating for the influence of the air gap between the transducer and the rod; the use of extreme points of the sensor conversion functions with the product when implementing measurements allows achieving the highest sensitivity to the parameters being measured; the developed method and device allow increasing the resolution of the transducer to geometric magnetic and electrical parameters, which are 2%, 5% and 8%, respectively. Conclusion: the developed method and device are of great importance for the further development of multiparameter methods for quality control of metal products, in particular when conducting express analysis of material blanks, quality control of the technological process of manufacturing products, as well as selective control of reliability of operation during their operation.