Design Of Single-phase Watt-hour Meter Based On TMR Current Sensor

China is the largest power consumption country in the world.The large base of electricity trading leads to even small measurement errors that can cause huge measurement unfairness.At this time,both the supplier and the demander hope that the accuracy of electricity measurement will be higher.Watt-hour meter is the basic tool of electric energy measurement.Its performance directly reflects the scientific level and quality of electric energy measurement.Current as a necessary parameter for meter to measure electric energy,the discussion of its measurement technology has always been active in the field of scientific research.Since physicists discovered the TMR effect,electrical engineers have also applied TMR devices to current detection.The current sensor based on TMR effect has outstanding performance in measurement range,sensitivity,power consumption,stability,miniaturization and integration,and has high engineering application value.This paper researches the single-phase watt hour meter based on TMR sensor,which is of some theoretical and practical value.In this dissertation,the working principle of TMR current sensor is analyzed,the frequency response characteristic of TMR current sensor is studied by using the method of system identification,and the conditioning circuit of TMR current sensor is designed to match the output signal range of TMR current sensor with the input signal range of metering chip.This dissertation shows the hardware design scheme of single-phase watt-hour meter,the type of the MCU chip R7F0C004,the measuring chip is RN8209 C,the MCU control circuit,measuring circuit and electromagnetic compatibility are introduced in detail.The software system adopts hierarchical and modular design scheme.The software system is divided into drive layer: system layer and application layer,which is convenient for later system maintenance,platform transplantation and function expansion.Finally the performance test of single-phase electronic energy meter based on TMR sensor is carried out,and the uncertainty of measurement results is evaluated.The results show that the measurement error of the electric energy meter designed in this paper is within ± 2%,and the uncertainty of the measurement result is less than 0.5172%.The meter meets the national requirements for 2.0 class electric energy meter,and the measurement result is reliable and has high practical value.