The Design And Implementation Of A Zero Flux Hall Current Sensor

Most domestic railway carriages use hall current sensors based on zero flux theory ascurrent surveillance sensors.Although variety of current waves including direct currentand alternating current can be measured,but unsatisfied temperature characteristic andinclining to be affected by environment temperature indicate that current measurement cannot be fulfilled accurately and reliably.A high temperature performance current sensor thusto be designed and implemented with a permalloy torus coil and a signal processingtemperature compensation circuit.This article gives details in the basic principles and structures of two different hallcurrent sensors.A mathematic model of the zero flux hall current sensor has been built andanalyzed in terms of negative feedback which provides the characteristics and errors of thesystem in order to reduce the measurement errors and improve the accuracy.Somefundamental characteristics and classifications of magnetic cores have been introducedand the length of air gap has been calculated.The magnetic flux density generated fromdifferent structures and materials has been simulated and compared using electromagneticsimulation software.A circuit including supply power module,signal processing moduleand power amplifier module has been designed and implemented.Experiment results on the bandwidth,linearity and temperature characteristics of asensor sample indicate that the total precision is within0.8%, the bandwidth is up to150kHz,the offset current is less than0.5mA and the thermal drift of output current is lessthan2.5%.The new designed zero flux hall current sensor meets the demand of currentmeasurement and is not affected by the interference from temperature.