Investigation Of The Magnrtic Field Sensor Made By Three Layer Magneto-Electric Composite Materials

Giant magnetostrictive materials have a lot of excellence, for example, highly capability of magnetostrictive, big output power, high energy density and so on. The magnetoelectric composite material is made by magnetostrictive and piezoelectric materials. The composite material has a lager mgnetoelectric transformation effect.We utilize the magnetoelectric product effect of magnetostrictive-piezoelectric laminate composite and fabricate a magnetic field sensor with 3-layer Terfenol-D/PZT/Terfenol-D laminate composite. The magnetic field sensor has a high sensitivity for measuring magnetic field.The magnetoelectric voltage coefficient of the laminate composite sensor can be calculated by means of equivalent circuit method. The magnetoelectric coefficient equation can describe the relation between input magnetic field and the output voltage, which is very import for design magnetic field sensor.Through establishing the experiment system, a series of static and dynamic experiments have been done for the magnetic field sensor. The static testing has shown that the magnetic field sensor works well when the amount of DC increases from 2A to 5A. Dynamic experimentation has ensured the effect of the bias DC and the frequency on the output properties for magnetic field sensor. The experimentation improves that the sensor's voltage is lager and magnetoelectric voltage coefficient changes less in low frequencies. We can find that there is about a linear relation between the sensor's output voltage and the input current when the amplitude and frequency of input magnetic field are changed. We have designed the signal processing electric circuit in order to read-out the intensity and the frequency quickly. The core of the control system is MCU(AT89S52) and the amplifier is MAX412 with low-noise and low-voltage. The filter is MAX291 with 8th-order, lowpass and switched-capacitor filter. The A/D conventer is the wide using AD1674 with 12 bits at present. We use 5 bits LED as the display part. The system contains other circuits also, for instance, electricity switching circuit and the driving circuit for the display part. We also designed the software of the system. The debugging of the signal processing system has been carried out and the debugging result shows that it worked well.