Study On Measurement Circuit With Low Power Consumption Of Resistance/ Capacitance Type Sensors

As the main methods and means of obtaining information in industrial production and scientific research,The sensor provides the necessary conditions and basis for people to explore new things,measure and control.With the continuous development of sensor technology,the application range of resistance type sensors and capacitance type sensors,which are two kinds of basic sensors,is more and more widely.However,in many areas,such as internet of things,passive wireless measurement and wearable equipment,which asks for sensors having a very low power consumption,only sensors with low power consumption can be used,which makes many existing resistance/capacitance type sensors can't meet the requirements.The power consumption of resistance/capacitance type sensors comes from their measurement circuit,so the key of low power resistance/capacitance type sensor is to design a measurement circuit with low power consumption.Because of this,the paper puts forward using RC square wave oscillation circuit as the measurement circuit of resistance/capacitance type sensor.Through the analysis and design with low power consumption and stability,the measurement circuit runs steadily with the power consumption below 1mW.In the end,this paper designs a resistance type magnetic sensor with the measurement circuit.The work in this paper is provided as follows:(1)Analyze the principle of the common measurement circuit of resistance /capacitance type sensors,and contrast their advantages,disadvantages and limitations.(2)Choose RC oscillation circuit as the measurement circuit of resistance /capacitance type sensors,and make a theoretical analysis and comparison on all kinds of RC oscillation circuits.Combining the experimental analysis and contrast,select the RC square wave oscillation circuit with CMOS inverter as the measurement circuit of resistance/capacitance type sensors at last.(3)Do a detailed analysis on the principle of RC square wave oscillation circuit with CMOS inverter,analyze the factors affecting the stability of the oscillating circuit and propose the corresponding solution when making low power consumption analysis and design.(4)Establish a synchronous acquisition and storage system,which uses for acquiring and storing power supply voltage data,ambient temperature data and output frequency data of RC square wave oscillation circuit with CMOS inverter.At thesame time,compile a data processing program with Matlab,and conclude the correlation between output frequency and supply voltage(or ambient temperature).(5)Design a resistance type magnetic sensor with TMR2501 and RC square wave oscillation circuit with CMOS inverter,which meets requirements of low power consumption.Experimental results show that the sensitivity of this magnetic sensor is 0.24kHz/mT,the resolution is 0.14‰,power consumption is less than 990?W with the measurement range of 0~30 mT.