Hardware Development Of Two Electromagnetic Sensor Signal Processing Systems

Electromagnetic sensor is a kind of sensor which converts the measured physical quantity into the induced electromotive force.It has high sensitivity,large measuring range and does not need special maintenance.It is widely used in automatic systems.This paper takes the electromagnetic flow sensor and the planar electromagnetic sensor as the research object,and studies the hardware design method of the measurement system.Electromagnetic flow sensors are widely used in industrial measurement applications because they are not affected by fluid density,temperature,pressure and other factors,and have the advantages of open flow and moving parts in pipelines.The output signal amplitude of the electromagnetic flowmeter is weak,and it is vulnerable to the electromagnetic interference from the surrounding environment under the actual working condition,so the SNR is low and difficult to pick up.According to the characteristics of the output signal of the electromagnetic flow sensor,a design scheme of signal conditioning and conversion circuit with high precision and low noise is proposed.According to the frequency range of flow signal,a two-stage fourth-order Butterworth anti-aliasing low-pass filter is designed to filter out high-frequency noise signals.Based on the 24 ?-? ADC design high accuracy sampling circuit.The electric conductivity measurement scheme of the electromagnetic flowmeter is proposed,which can be synchronized with the flow measurement without affecting each other,and the digital signal processing method based on energy attenuation is adopted to realize the electric conductivity measurement and air tube detection of the measured flow body in the pipeline.Finally,water flow calibration experiment and conductivity measurement experiment were carried out on the developed electromagnetic flowmeter transmitter.The experimental results showed that the developed electromagnetic flowmeter had a maximum relative error of 0.136% and a maximum repeatability of 0.044% within the range of flow velocity of 0.5m/s?5.0m /s,and the system accuracy was better than 0.3.The conductivity measurement system can meet the measurement accuracy of 3% within the conductivity range of 100?S/cm?3000?S/cm.Planar electromagnetic sensor has the characteristics of high sensitivity,large measuring range and fast scanning and detection,and is widely used in medical treatment,ecological environment,aerospace and other fields.In order to meet the requirements of planar electromagnetic nondestructive testing system for simultaneous acquisition of multi-channel high-speed signals and real-time data processing,a dualcore processor scheme based on FPGA+DSP was designed to build a digital signal processing system.As the main controller,DSP is responsible for controlling the working state and data communication of the system,while FPGA,as the subordinate controller,mainly realizes the generation and control of timing sequence and the processing of algorithm.A high frequency sinusoidal excitation scheme based on direct digital synthesis technology is designed,which has the characteristics of high precision,good stability and adjustable frequency.The design of high speed signal conditioning and acquisition circuit with high precision and low noise,including full differential amplifier circuit,passive anti-aliasing filter circuit and high speed data acquisition and conversion circuit,can realize the data acquisition and conversion of multi-channel signals in real time.