Design of a High Accuracy AC Resistor Voltage Divider

作者： GOZ Electric 时间：2024-11-15 09:31:45 阅读：13

This paper mainly discusses the principle, design and calibration of a high-accuracy, multi-range AC resistor voltage divider. It studies the AC resistor voltage divider with a voltage range of 0.5V to 600V and a frequency of up to 1MHz, and realizes the expansion and application of the AC voltage proportional measurement range based on the existing technology. And through the broadband AC voltage signal sampling measurement technology and synchronous sampling trigger technology, the back-end impedance of the voltage divider is matched with the gain buffer amplifier to realize the calibration test of the high-accuracy AC voltage divider. With the development of measurement technology, the range expansion of proportional measurement is particularly important. The use of proportional standard devices can unify the measuring instruments into a standard form. Its structure is simple and reliable, and the measurement accuracy is higher than that of direct instruments. In order to solve the problem of untraceability in the process of AC voltage proportional value transmission, it is necessary to expand the existing AC voltage proportional value measurement range and develop corresponding metrological standards and metrological calibration technology. The main difference between the broadband AC resistor voltage divider developed in this paper and the existing DC resistor voltage divider is the influence of the time parameters of the resistor device in the circuit and the various parasitic capacitances in the line on the phase angle error of the voltage divider. In order to reduce the influence of parasitic capacitance introduced by resistors, the equipotential shielding voltage divider adopts a capacitive voltage divider design instead of a resistive voltage divider design. During the test, unlike the DC resistor voltage divider, the broadband AC resistor voltage divider uses a sampling device for calibration test, and the impedance matching of the buffer amplifier and the input end of the sampling device ensures the accuracy and reliability of the measurement results.

2 Basic principles of resistor voltage dividers

The broadband resistor voltage divider is a proportional device used for precision AC voltage measurement. It can proportionally convert AC high voltage signals into low voltage signals that can be measured by digital instruments or sampling devices in the DC to 1MHz frequency range. The basic principle of the resistor voltage divider is relatively simple. The output voltage value is equal to the product of the proportional value of the voltage divider resistance and the input voltage. However, in actual use, especially in AC circuits, the resistor voltage divider is more affected by the load capacitance. In order to offset the frequency response characteristics caused by the load capacitance, the circuit adds load capacitance, equipotential shielding capacitance, and resistor compensation capacitance. The model principle is shown in the figure to reduce the contribution of stray capacitance to the phase angle error of the voltage divider. Through simulation experiments, combined with the influence of capacitors on the measured value of the voltage divider ratio

error, the initial capacitance of each capacitor is determined one by one, and then accurately adjusted in subsequent actual tests, and finally reliable test results are achieved.

Conclusion

In summary, the calibration analysis sampling system is used to calibrate the 1MHz high-accuracy AC resistor voltage divider. The high-speed data acquisition card in the device has a 60MHz internal clock, and the sampling rate can reach up to 15MHz. The method of synchronous sampling using dual channels and sharing the same clock for two channels is very suitable for broadband voltage measurement, which greatly solves the problem of proportional measurement range expansion in electrical measurement, and lays the foundation for the subsequent research on AC voltage proportional traceability technology and the expansion of the system AC voltage proportional value transmission coverage.