Remote Impedance Measurement with a Long Connecting Line (Review)

This study analyzes the existing solutions to the problem with remote electric-impedance measurements in which a long line connects the measured object to the measuring instrument. It is specifically the case in an experimental study of the impact of test conditions on high-frequency properties of dielectric and magnetic materials and characteristics of radio components when the location of a specified object near the measuring instrument and the operator is impossible. The main criterion was the possibility of selecting the measuring frequency-to-line length ratio while maintaining the measurement accuracy. The subjects of the analysis are the existing inventions grouped according to the similarity of the methods for recording the parameters of line, two types of present-day impedance meters, and two modifications of one of them. It is shown that the known inventions and impedance meters generally have limited capabilities, and only the mentioned modifications can serve as the basis for measuring instruments that are able to cardinally solve the problem.