C. Schott

Linearizing integrated Hall devices

This paper shows how modern integrated silicon Hall devices can be linearized without any additional error correction. Several non-linearity effects are studied and by adequate means either eliminated or mutually compensated. Experimental results demonstrate that the remaining non-linearity in a magnetic field of up to 2 T can be decreased to less than 1%. Together with low noise characteristics and extraordinary long-term stability, these devices are ideal sensors for low cost, high accuracy applications in low and medium magnetic fields.

Nonlinear effects in magnetic angular position sensor with integrated flux concentrator

We studied nonlinear behaviour of the angular position magnetic field sensor that consists of CMOS integrated circuit chip and a thin ferromagnetic disk. Developed numerical 3D model was compared with experimental results with a good agreement. Obtained numerical results were used to determine the linear magnetic working range of the sensor. We also calculated the nonlinear error for the disk positioning relative to the Hall elements and found 3.3% of error for the 10 /spl mu/m displacement. We proposed a simple amplitude calibration to strongly reduce nonlinearity coming from misalignment to 0.3% of the full scale. Additional nonlinearity from Hall elements has been discussed. The offset and sensitivity mismatch, contribute to the nonlinearity of the sensor less than 1/spl deg/.

Single-chip 3-D silicon Hall sensor

A silicon Hall device for high accuracy three-axis magnetic field measurements is presented. Its unique geometry allows the extraction of the information about the three magnetic field components simultaneously and at exactly the same point in space. Electrical connection consists of only two energy supply contacts and only four sense contacts. The entire decorrelation of the Hall electrode potentials and the retrieval of the three flux density components is performed by a simple one-stage differential amplification unit. A series of prototypes with the dimensions of the active area of 50, 100, 300 and 500 μm was realized. Sensitivity for the two axes parallel to the chip surface is between 50 and 830 V/AT and for the perpendicular one between 17 and 900 V/AT. Input resistances vary from over 40 kΩ for the small device to less than 1 kΩ for the largest. The active region of the devices is buried under the surface, so that the sensors feature low noise and excellent long-term stability.

A new two-axis magnetic position sensor

Describes a new contactless sensor, which measures the position of a magnet along two axes. The sensor is inherently non-sensitive to the magnet movement along the third axis, temperature variations and aging, and does not require calibration. This is achieved by transforming a translation of the magnet into a rotation of a magnetic field, and by measuring the direction of the magnetic field rather than its strength. The direction of the magnetic field is then measured by two two-axis Hall sensors.

Bridging the gap between AMR, GMR, and Hall magnetic sensors

By integrating a magnetic flux concentrator (IMC) at the surface of a Hall magnetic sensor, we can dramatically improve its characteristics. Here we compare the performance of a new IMC Hall sensor ASIC with the performance of traditional magnetic field sensors, such as AMR, GMR, and conventional Hall sensor ASICs. We find that the detectivities of AMRs and GMRs for AC magnetic fields are much better than those of Hall ASICs; for low-frequency fields, the performance gap is smaller; but for DC fields, the resolution of the IMC Hall ASIC is much better than that of GMRs and approaches the resolution of a nonswitched AMR. Also according other parameters, the IMC Hall ASIC is positioned in the gap between AMRs, GMRs, and the conventional Hall ASIC magnetic field sensors.

Microsystem for high-accuracy 3-D magnetic-field measurements

Abstract A new microsystem for very high-accuracy magnetic measurement of all three field components is presented. A single silicon die incorporating eight sensor devices is mounted on a support and then cut. This galvanic separation is essential, since the applied technology of vertical Hall devices yields very high-quality devices, but does not provide for the isolation. In this way perfect alignment of the sensing directions of the sensors is achieved. All sensors are arranged in such a way that their signals can be combined to represent the x , y and z components of the magnetic flux density in the centre point of the system. The active volume is about 2 mm × 2 mm × 0.2 mm and the precision of the alignment is higher than 0.1 °. Measurements of cross-current and cross-sensitivity between the two in-plane axes of an identical but uncut sensor prove the necessity of cutting for achieving an accuracy of better than 1‰.

Planar Hall effect in the vertical Hall sensor

The planar Hall effect is theoretically and experimentally studied in the vertical Hall sensor (VHS). Compared to silicon plate-shaped devices where experimental and theoretical value correspond well, the experimental value for the vertical Hall device is about 10 times smaller than theory predicts. This fact is explained by anisotropy effects and by the unique self-compensating structure of the device. Thus, magnetic field transducers built with devices of this structure are particularly adapted to the measurement of magnetic fields with more than one component.

Realised examples of microsystems and their applications

Figure 2: Implementation ofthe vertical Hall device in microelectronic processes3. applied. This kind of sensor can be produced on a silicon wafer using microelectronic-like technologies. Despite the relatively low sensitivity of silicon devices compared to moresophisticated materials, these components are well suited for mass production at very low cost and their longterm stability and signal-to-noise ratio are excellent2. Vertical and cylindrical Hall devices The Hall effect produces a voltage proportional to the magnetic field Magnetic sensor microsystems