Magnetic Sensor Works Despite Interference. A 3-D magnetic field sensor has been developed by the Fraunhofer Institute for Integrated Circuits IIS in Erlangen that can work without screening. Several sensors are arranged in a cell in such a way that they can measure all three components of a magnetic field in one place. If two such cells are placed on a chip, the sensor measures not only the magnetic field, but how it changes with position. According to IIS team leader, Dr Han-Peter Hohe, “This sensor enables us for the first time to identify magnetic interference fields as such and to separate them from the useful field. The sensor works perfectly even when the interference field is considerably larger than the useful field, there is therefore no need for shielding.” ...

Articles, Papers and References

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C.Schott, Burger F., Blanchard, L. Chiesi, Modern Integrated Silicon Hall Sensors, Sensor Review, Vol.18, No.4, 1998, pp.252-257.

Abstract - The new developments in silicon Hall sensors are highlighted. First, basic components made by microelectronic technology are explained. They lead to the development of high accuracy vectorial magnetic probes. Then examples of new application like angular position sensor and current measurements are illustrated. Finally, new concepts in order to increase the detectivity using magnetic chopping are demonstrated.

A.Häberli, M. Schneider, P. Malcovati, R. Castagnetti, F. Maloberti, and H.Baltes, 2D magnetic microsensor with on-chip signal processing for contactless angle measurement", IEEE Journal Solid-State Circuits , vol. 31, pp. 1902-1907, 1996.

Abstract - The reported CMOS microsystem is the key element for accurate angle measurements. In combination with a permanent magnet it is used for various wear free angular positioning control systems for automotive and industrial applications covering the full 360 degree range. The integrated system includes a two dimensional magnetic microsensor (30 x 30 m2 active area), offset compensation and signal conditioning circuitry. A novel approach for the angle calculation is presented using an on-board incremental ADC. A bitstream representing the angular position of the applied permanent magnet is provided at the system output. The system achieves a one degree angular resolution with 9 mW power consumption and a permanent magnet of 100 mT. The chip is fabricated in a generic 2 m double poly, double metal CMOS process and covers an area of 2.6 x 4.1 mm2.

P. Malcovati, F. Maloberti, A. Pesucci, and M. Poletti, A 12-bit A/D interface for a 3D magnetic sensor, Proceedings of IEEE International Symposium on Circuits and Systems (ISCAS `97) , Hong Kong, pp. 1-4, 1997.

Abstract - This paper presents a high resolution low-power smart system for 3D magnetic field monitoring. The magnetic sensors, integrated on-chip, need a bias current of a few mA to achieve the required resolution. Nevertheless, the proposed 12 bit A/D converter allows pulsed operation of the sensors with a duty cycle as low as 4 10-5, thus keeping the system power consumption below 1 mW. The A/D converter operates with 500 kHz clock frequency and achieves a DNL below 0.2 LSB and an INL below 0.5 LSB in worst case simulations. A prototype of the system has been integrated in a 1.2 mm CMOS technology.

A. Häberli, M. Schneider, P. Malcovati, R. Castagnetti, F. Maloberti, and H. Baltes, Magnetic microsensor with on-chip signal processing for contactless angle measurement", Proceedings of IEEE International Solid-State Circuits Conference (ISSCC `96) , San Francisco, USA, pp. 332-333, 1996.

Abstract - We present a CMOS microsystem which is used for accurate contactless angle measurements in combination with a permanent magnet (1 degree measured resolution). The integrated system includes a 2D-magnetic microsensor, temperature and offset compensation circuitry as well as signal conditioning for the angle calculation.

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GMR Sensors Data Book, NVE Corporation, 2003