Design On Current Measurement System Of Balanced Magnetoresistive Sensor

Along with the development of technology,low current play a more important role in many fields such as industry, production and life. So the technology of monitoring and detecting low current has emerged. Based on the feedback control theory, the design in this paper has achieved process to small current with accuracy and fast using DSP.The principal of the feedback system of small current detecting are as followed: signal acquisition module, controller of TMS320F2812, amplifier module, feedback module. The system works the following way: firstly, when the system is powered on, magnetic sensor will produce the electrical potential which will be amplified by AD620. Secondly, the voltage from AD620 will be sampled, quantized by A/D conversion in DSP2812, filtered and PID digital processed using software. Lastly, the voltage will be transferred into current and the output current will be sent back to magnetic loop which will neutralize the edge magnetic field produced by current-carrying wires, then the whole system will forms the closed loop negative feedback circuit.In order to measure the current with noncontact and improve the stability, the system uses the magnetic loop with clearance. Using DSP and set/reset circuits enhance the ability to resist interference, improve the accuracy and process more quickly.