Electronic Compass Circuit KMZ52 Magnetic Field Sensor

Electronic compass circuit used in the main kmz52 magnetic field sensor integrated in the market, is there I do not know, but a different application also circuit more complex does not count eagle prepared with schematic drawings, PCB drawing, measuring and testing on fluoroscopic images there.

The aim of the project is to verify the possibilities of measuring the magnetic field using the KMZ52 magnetic field sensor and then to create a prototype device for measuring mag. the Earth’s field, i.e. the electronic version of the compass, from which the azimuth can be determined.

To measure mag. in the field, the KMZ52 integrated circuit is used. To measure azimuth, it is necessary to measure the mag density. field in two axes, the x and y axis. Azimuth can be determined by comparing the magnitudes of the densities from individual directions. These are magnetoresistive sensors. The sensor consists of a resistive bridge made of a material that changes resistance depending on the mag density. field. The output from this bridge density mag. field is converted into a differential voltage.

Since the output differential voltage of the sensor is very weak, it is necessary to connect about 1.5 mV to the output of the operational amplifier in a differential amplifier type connection, where the gain is determined by the ratio of the resistances. Another necessary condition is the compensation of the sensor’s offset, since it is several times larger than its own useful signal. Offset compensation is carried out using an integrated compensation coil located in the sensor.

For ideal compensation, a 1A current with alternating polarity must flow into this coil for a very short time on the order of nanoseconds. When the current flows through the coil, a magnetic field is created around it. And by changing the polarity, the direction of the magnetic field created is changed, thus eliminating the offset error. The timing and triggering of the pulses is the responsibility of the processor, which acts only as a “clocking” signal generator. The function can be better seen from the graph below, where the green waveform is the trigger signal generated by the processor and the red waveform corresponds to the short pulses in the compensation coil.

KMZ-52 Magnetic Field Sensor

KMZ52 extremely sensitive magnetic field sensor, employing the magnetoresistive effect of thin-film permalloy. The sensor contains two magnetoresistive Wheatstone bridges physically offset from one another by 90° and integrated compensation and set/reset coils. The integrated compensation coils allow magnetic field measurement with current feedback loops to generate outputs that are independent of drift in sensitivity. The orientation of sensitivity may be set or changed (flipped) by means of the integrated set/reset coils.

Source: Tomáš Lembard, UREL, FEEC, VUT Brno urel.feec.vutbr.cz alternative link: