IMPLEMENTATION AND EXPERIMENTAL RESEARCH OF THE TEST AND REFERENCE SIGNALS DIGITAL GENERATORS FOR IMPEDANCE MEASUREMENT IN WIDE FREQUENCY BAND

Abstract

The structure and design of a new unified basic measuring module, which is intended for constructing broadband means for determining the impedance parameters are described. This module was used by us to study the important metrological characteristics of digital test and reference signal generators, as well as the entire measuring channel, which used in such devices. The features of the created instrument are the possibility of highly-discrete and precise regulation of the amplitude of the test signal, regardless of frequency in the range up to 1 MHz by paired integrated digital-to-analog converters operating on direct current, and the possibility of obtaining additional coherent reference signals that are phase-controlled relative to the test signal with an accuracy of no worse than a few nanoseconds. The results of experimental studies of the regulation characteristics and a detailed study of possible sources of errors in the formation of quasi-sinusoidal test and reference signals in the ranges of their possible states are presented. The sources and the magnitudes of the modular and phase errors of the new measuring channels with direct conversion of the impedance parameters and with compensation of the phase shift of the signal in the measurement object, as well as channels with balancing the bridge circuit modulo and phase, which are based on the developed digital generators, have been determined. Ways to reduce the errors are indicated. It have been showne the possibility of obtaining errors modulo and tangent of the phase angle of the measurement object is not worse than 0.1% of infralow frequencies up to 1 MHz and the possibility of creating a precision ethalons of the tangent of the phase angle for the industrial frequencies. At frequency of 1 kHz, the error of the instrument under study, on the parameter which is quadrature relatively the main, did not exceed 0.001%.