Meleshchuk D. Precision bridges of changeable current for measurement of platinum resistance thermometers impedance in frequencies diapason

Subject of inquiry: measurement of active resistance of platinum thermometers on an alternating current. Purpose of the work: theoretical determination of frequency errors of platinum resistance thermometers (PRT) and elaboration of precision thermometer bridges of an alternating current for experimental determination of frequency dependence of an active resistance of PRT. Methods of inquiry: methods of a theory of complex variable functions, numerical methods of a mathematical analysis, a theory of series, a theory of errors, methods of a probabilities theory and a mathematical statistics. Theoretical and practical results and novelty: a problem of dependence of a frequency error of platinum resistance thermometers on a temperature being measured is investigated; a methodical error of determination of an unbalance value in double-circuit bridges at application of a variation balancing method is investigated; a new approach to a problem solution of measurement accuracy increase of alternating currentbridges with a measuring circuit on digital-to-analog converters, which is based on variation calibration of digital-to-analog converters, is found. Precision bridges of an alternating current for an active resistance measurement in a range of frequences are created on the basis of elaborated structural circuits. Subject and degree of introduction: results of operation are introduced at creation of a precision thermometer bridge of an alternating current CA 300 and they permitted to increase its speed of response and technical-and-economic indicies. Sphere of application: precision electrical measurements.