Design And Implementation Of Embedded High Precision Voltage Standard Source

With the development of science and technology,the requirements for the accuracy of digital multimeters are getting higher and higher.Correspondingly,the accuracy requirements for the calibration source for calibrating digital multimeters are also getting higher and higher.Aiming at the problems of poor stability and low resolution of current domestic AC voltage calibration sources,this paper has carried out research on multimeter calibration technology and designed an AC voltage standard source that can meet the calibration requirements of six and a half multimeters.The current situation that high-precision measurement and calibration instruments rely on imports has been resolved.The main research contents of this article are as follows:Firstly,the overall scheme design of the AC voltage standard source is completed.The standard source consists of a high-precision DC reference,a broadband amplification module,and a sinusoidal signal generator.According to the accuracy requirements of each part,the error theory is studied,the source of the error of the system is analyzed,and the error distribution of the system is completed.In order to improve the stability and accuracy of the output voltage,a control system based on negative feedback is designed;In order to improve the rapidity of the output voltage,a feedforward link is added to form a double closed-loop system based on feedforward-feedback control.Secondly,the design of the hardware circuit is completed.Aiming at the requirements of the system index,a strategy for improving the accuracy of the AC voltage standard source is proposed.In order to improve the resolution of the DC voltage reference source,the dual PWM modulation method is studied.At the same time,the stability of the DC reference is improved by the research on the temperature compensation strategy and the accuracy improvement strategy of the inverter circuit.The use of deep negative feedback technology and the introduction of a multi-stage amplifier circuit based on common-common-emitter amplifiers improve the stability and frequency range of the power amplifier circuit.Thirdly,a strategy for improving the accuracy of the sine generator is proposed.In order to suppress the truncation error of the sine wave generator and improve the frequency resolution,the random perturbation technology and ROM compression technology were studied.Using FPGA as the controller of the sine wave generator,the operation efficiency and the frequency range of the output sine wave were improved.At the same time,the control methods of relays and analog switches and the system's command parsing protocol are also studied.Finally,the joint debugging of the system was completed,the upper computer test software was written,an automatic test system based on the upper computer and the FLUKE8508 A eight and a half digital multimeter was built,and the system's experimental research was carried out to test the long-term working stability of the system.The error compensation algorithm is studied,and a two-dimensional error compensation algorithm for AC voltage is proposed.The final test results show that the resolution of the AC voltage standard source designed in this subject can reach 1?V,and the accuracy can reach 0.03%,which can meet the calibration requirements of six and a half multimeters.