Abstract:
A magnetic flux sensing device which employs Magnetoresistive sensor has been developed for the measurement of magnetic flux of semiconductor devices.
The magnetic flux measuring system consists of sensing unit, analogue-to-digital converter, and microcontroller with intelligent display unit. The magnetoresistive sensor (HMC 1021) is used which has a sensitivity of about 5μV/nT at 250C. The output pins of the HMC1021 are interfaced with a differential amplifier circuit. The differential amplifier is constructed via buffer amplifiers (op-amps) that produce the difference signal. The buffer amplifier is linked between the differential amplifier and analog-to-digital converter (ADC) to improve the impedance between differential amplifiers and ADC. The analog output voltage of the amplifier is fed to an Analog-to-Digital Converter (ADC). The microcontroller processes the data from the ADC, perform the conversion process by programming the characteristics equation obtained from the output of the buffer and the corresponding voltage. The output of the ADC makes American Standard Code for Information Interchange (ASCII) code to be displayed on the intelligent display unit.
The developed magnetic flux meter was calibrated using standard fluxmeter, 480 Model meter to determine the accuracy and precision of the system.
Testing was carried out to evaluate the performance of the developed fluxmeter. From the results obtained, it was observed that the test was successful as the fluxmeter can measure within the range 0.1nT to 1000nT, which is comparable to 480 Model fluxmeter purchased from abroad. The results obtained during testing of the fluxmeter reveal that with the properly designed control sequence and the implementation of a “Set/Reset” magnetizing procedure to compensate the offset of the sensor, the developed fluxmeter is able to provide good quality data.
