Reference calibrator of electrical voltage in the frequency range 0.1–30.0 MHz
Yu. D. Bolmusov, V. A. Martinov · Izmeritel`naya Tekhnika · 2024
The park of high-precision measuring instruments of alternating voltage – working standards of the 1st and 2nd category in the frequency range 0.1–30.0 MHz is considered. It is noted that thermoelectric voltage converters, which were developed more than 30 years ago, have exhausted their life and do not meet modern operational requirements, are used as a working standards of the 1st category without alternative. An alternative to sets of thermoelectric converters in the frequency range 0.1–30.0 MHz can be AC voltage calibrators. However, in the specified frequency range, there are no AC voltage calibrators – working standards of the 1st category. For operation in the frequency ranges of 0.1–30.0 MHz and voltages of 1·10 -3 –10 V, a high-frequency AC voltage calibrator H5-10 has been developed with characteristics that exceed the requirements for working standards of the 1st category. The principle of construction, characteristics and operational capabilities of the H5-10 calibrator are described. When constructing the calibrator, a method was used to equalize the amplitude of the high-frequency voltage with the known amplitude of the low-frequency sinusoidal voltage by amplitude detection. The high-frequency sinusoidal voltage in the calibrator is generated by a frequency synthesizer using direct digital synthesis and a bandpass filter system. The accuracy and stability of the amplitude of the high-frequency voltage at the output of the calibrator are supported by an automatic control system based on the principle of mutually-inverse conversions using a two-diode integrated assembly of identical Schottky diodes. The low-frequency stable voltage for the reference input of the automatic control system is formed by a low-frequency calibrator with a frequency of 10 kHz. This calibrator generates an alternating voltage in the range of 0.1–10.0 V with a harmonic coefficient of less than 0.01 % and a discreteness of amplitude adjustment of 0.001 %. The low-frequency calibrator is built on multiplying digital-to-analog converters by the method of digital synthesis of a sinusoidal voltage of a stable constant voltage measure of 2.5 V. The nominal output voltages of the calibrator H5-10 in the range of 0.1–10.0 V are reproduced by an automatic control system, and in the range of 1–100 mV by scaling using a voltage divider. The main areas of application of the developed N5-10 calibrator are the verification and calibration of electronic voltmeters, voltage calibrators, multimeters and voltage transducers used as working standards of lower-level categories.