Research And System Development Of AC/DC Excitation Measurement Method Of Strain Sensor

Strain force sensor is widely applied in scientific experiments and industrial production.However,the noise interference are different in different applications;Thus,when the frequency band of noise overlaps with that of the measured force signal,the measurement accuracy of the sensor will be greatly reduced,or even be false.Hence,in order to meet the measurement requirements of strain force sensors in different noise environments,the work in this dissertation mainly studies the AC/DC excitation measurement method of strain force sensor,and develops the corresponding digital AC/DC excitation measurement system to achieve high-precision measurement.First,based on the basic principles of AC and DC excitation measurement of strain force sensor,the digital AC and DC excitation measurement schemes and signal processing algorithm flow are proposed,a solution for the problem of parasitic parameter interference of long wires under AC excitation measurement is presented,noise suppression performances of AC/DC excitation measurement methods are analyzed and compared,and the corresponding simulation and verification are carried out.Second,a multi-channel digital strain sensor AC/DC excitation measurement system is developed by using the DSP chip TMS320F28335 as the core.For the system,The AC /DC excitation mode is optional and the excitation frequency is digital adjustable;Eight analog input/output measurement channels are provided.The analog input adopts four / six wire system optional scheme,and adopts multi-channel synchronous sampling control to realize 16 bit high-precision measurement Strain force sensor provides flexible and high precision measurement platform.Third,a noise adaptive AC/DC excitation software measurement method is proposed and implemented through programming based on the developed AC/DC excitation measurement system.Firstly,the system uses DC excitation mode to collect the field noise and analyze the frequency spectrum.Then,the excitation mode and frequency are selected to calculate the corresponding working parameters.Then the corresponding excitation measurement process is entered to realize the automatic selection and measurement of excitation mode.Last,taking S-type strain type force sensor as an example,the static calibration and dynamic measurement experiments of the system with or without strong low frequency interference are carried out.The results show that the maximum measurement error is more than 2.5% when the AC excitation noise is less than 0.5% and the maximum measurement error is less than 2.0% when the AC excitation noise is less than 0.5%.The dynamic measurement results show that the DC excitation method cannot overcome the interference of strong low frequency noise,while the AC excitation measurement method can effectively overcome the interference.In summary,the AC / DC excitation measurement method of strain type force sensor and the developed system have high measurement accuracy and strong practical value.Considering that the frequency band of AC excitation measurement method is limited by AC excitation frequency,this study can provide a flexible method for strain force measurement in different applications.