Accurate 3D Measurement of Magnetic Fields for Automotive Gear Selector : Page 5 of 6

October 10, 2016 //By Hannes Birk and Sigmund Zaruba, Infineon Technologies
Accurate 3D Measurement of Magnetic Fields for Automotive Gear Selector
The TLE493D-W1B6 magnetic sensor provides accurate three-dimensional (3D) magnetic field measurement, extremely low energy consumption and integrated magnetic field alert functionality. Potential automotive applications for this technology are gear selectors, control elements, top column modules and applications involving linear movements or angle measurement.
switch in each of the six selector positions. These six Hall switches can be replaced by a single TLE493D-W1B6 3D sensor (Figure 4 right).

Figure 4: Gear selector realized
with six Hall switches (left) and a single 3D
magnetic sensor (right)

For a robust magnetic design, the following parameters should be used:

  • Magnet shape: Cuboid shaped (7 x 5 x 3 mm)
  • Magnet material: NdFeB
  • Remanence: 1 T
  • Sensor: TLE493D-W1B6
  • Air gap between sensor and magnet: 4 mm
  • Magnetization: Axial
  • Lever arm: 1.3 cm
  • Swept angle: 0 ... 30 °
  • Six positions result in a resolution of 6 ° per position

The parameters above allow linear behavior between the mechanically deflected angle and the calculated spherical angle Theta (Ɵ). The spherical angle is calculated from the sensor’s x, y, and z components (Figure 5).


Figure 5: Unambiguous position determination
with a 3D magnetic sensor

This allows the angle to be determined unambiguously, which in turn enables an unambiguous determination of the selector position. A detailed description (application note) is available at www.infineon.com/3dmagnetic.

Functional Safety

The TLE493D-W1B6 is also equipped with test functions that make possible malfunction detection during operation, allowing the complete sensor signal chain to be assessed at any time. The test delivers a defined value that the microcontroller can compare with the expected value. If the expected value is obtained, the master does not need to initiate further measures. Test times are significantly lower than 1 ms.

Alert Function

A further intelligent feature of the TLE493D-W1B6 is the magnetic field alert. For all three magnetic field directions, a corridor can be determined in milliTeslas for magnetic field strength. The magnetic field is cyclically measured in the set mode and compared with this corridor. If the measured magnetic field value remains within the corridor in all three directions, the sensor suppresses the interrupt signal. If the measured magnetic field value exceeds the upper corridor value or falls below

Design category: 

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