METHODS OF INCREASING THE ACCURACY OF MEASUREMENTS OF THE PARAMETERS OF TWO-COMPONENT TWO-TERMINAL NETWORKS CONNECTED IN A PASSIVE MEASURING CIRCUIT ELECTROMAGNETIC MEASUREMENTS
V. G. Evseev, M. Krysin · 2007
Research on the measurement of the parameters of two-component two-terminal networks is being carried out in all the industrial countries of the world. However, it has not so far been possible to achieve high accuracy and high speed of response simultaneously. Thus, in transformer bridges with tight inductive coupling, high measurement accuracy is achieved at the price of a loss in speed of response, while bridges with coordinated discharge balancing, which have a high speed of response, are inferior to transformer bridges in accuracy. In direct-conversion instruments, high measurement accuracy can only be achieved when operating with single-component (or high Q-factor) R, C, L-two-terminal networks, which limits their wide application, for example, for operation with sensors having a complex impedance. One can measure the parameters of a two-component two-terminal network, connected in a passive measuring circuit, using the amplitude-phase, amplitude and phase methods [1]. The drawbacks of these methods include the effect of the frequency of the supply voltage on the result, and interference which occurs during the measurement. The methods of measuring the parameters of two-component two-terminal networks proposed in this paper enable the effect of the supply-voltage frequency to be eliminated, and the system employed also considerably reduces the interference. The amplitude-phase method of measurement consists of generating effective values of the currents, taken from the two-terminal network being investigated and from additional two-terminal networks, similar, respectively, to the resistive and reactive components of the two-terminal network being investigated, and also the generation of signals proportional to the phase shifts of these currents with respect to the generator voltage. If a sinusoidal signal is applied to a standard two-terminal network R0, the two-terminal network ZX = RX + jXX being investigated, and a standard two-terminal network X0 connected in parallel, the following currents, respectively, will flow through them: ¶1 = ≤ /R0; Measurement Techniques, Vol. 50, No. 9, 2007