A set of high-frequency thermoelectric voltage converters with frequency-error compensation

High-frequency AC voltage measurement instrumentation fi nds limited application in the radio-electronic and defense industries, owing to considerable measurement errors induced by the parasitic reactive parameters of the measuring circuit. The pressing problem of enhancing the accuracy of RMS AC voltage measurements at frequencies exceeding 100 kHz is addressed herein. To resolve this problem, a method for compensating the frequency error of high-frequency thermoelectric voltage converters has been developed. For this purpose, a set of high-frequency thermoelectric voltage converters with frequency-error compensation has been developed and manufactured. The set comprises eight thermoelectric AC voltage converters designed for the following nominal voltage values: 0.5, 1, 2, 3, 5, 10, 20, and 30 V. The converters with nominal voltages from 1 V to 30 V incorporate additional resistors and adjustable structural capacitances controlled by a micrometric mechanism. The frequency-error compensation is described based on an analysis of the equivalent circuit as a section of a coaxial line with distributed parameters. The measurement equation is derived, the equivalent electrical circuit is presented, and experimental tests of the converter set are described. The measurement uncertainty of AC voltage using the developed converters is estimated. Based on the test results, it has been established that after individual capacitance adjustment, the relative error of AC voltage measurement did not exceed ±0.04 % at a frequency of 100 kHz and ±0.25 % in the frequency range of 1–30 MHz. At a coverage factor of two, the expanded uncertainty of the measurement results for converters with nominal voltages of 0.5–30 V at 100 kHz was 0.02 %. The obtained data confi rm the prospects of using the developed converter set as a secondary standard for the verifi cation of AC voltage measuring instruments.