OPTIMIZATION OF BALANCING IN A BRIDGE MEASURING CIRCUIT WITH A DIFFERENTIAL CONDUCTOMETRIC SENSOR

Abstract

The article is devoted to solving the problem of the occurrence of an additive error in determining local changes in the electrical conductivity of electrolyte solutions under conditions of changes in the background electrical conductivity of the measurement medium, which often occurs in biosensor and other systems with a differential pair of conductometric transducers, if their electrical parameters are not identical. The goal is to provide a deep suppression of the influence of background changes with significant differences in both reactance and active resistance in the transducers of a pair of sensor. The essence of the issue, the causes and mechanism of this type of error, as well as the methods and means of its reduction, developed earlier, are briefly considered. A diagram and description of the structure of a differential conductometric channel of a biosensor system based on an AC bridge, an algorithm for its balancing operations by controlling the module and phase of the test voltage, as well as a vector diagram of currents and voltages in the bridge circuit during this process. The balancing of the bridge has been was modeled analytically, bringing it to a quasi-equilibrium state, in which changes in the background electrical conductivity do not change its output signal. Additional operations for balancing the bridge are determined to achieve such a state with significant differences in both capacitances and active resistances in the impedances of a pair of conductometric transducers of a differential sensor. The results of experimental studies of the suppression of the influence of changes in the background electrical conductivity of a solution in a differential conductometric channel with using its computer model and experimental sample of a conductometric instrument with an electrical equivalent of a differential sensor are presented. A comparison of the results obtained and the corresponding data for balancing bridge circuits by previously developed methods is given. References 16, figures 3, tables 3.