Angle sensors

To sample the settling flux directly, free-floating multiple-sample programmable sediment traps (Pro-Trap) were deployed at all three fjords for about 16 h at each time (trap depth 60 m). The Pro-Trap system consists of four polyvinyl chloride (PVC) sediment tubes, each of 0.018 square meter exposed area (cylinder height of 80 cm, trap aspect ratio A 4 5.3), mounted on a stain-less-steel frame. Depth and angle sensors allowed defining the position of the traps in the water... 

The vision of braking and steering by wire will demand new, extremely reliable sensors. Even in early implementations of steer-by-wire systems, in which manual control can override any system failure, more than one sensor is normally used for the sake of redundancy. Many of the sensor principles required are already established in the market, including steering-angle sensors (e.g., for vehicle dynamics control) and pedal-position sensors. Mechanical action or feedback control, however, will drive the emergence of torque and force sensors. 

Some sensors include a second metallization layer to integrate a planar coil. Its additional field can be used as a flipping field for offset reduction or as a closed-loop compensation to keep the transfer curve at maximum sensitivity, what is especially necessary for low-field applications. In a third application, angle sensors, planar coils generate an auxiliary field to expand the measuring range. 

Magnetoresistive sensors can cover the whole spectrum of magnetic-field sensor applications, because they can detect both, the strength and the angle of the sensing field. In this section I explain their application as angle sensors. 

Fig. 5.7.3 Principle and layout of an AMR angle sensor for 180° measuring range...

Today s angle sensors based on the AMR effect allow an accuracy of better than 1° to be obtained over the full measuring range and for temperatures up to +150°C. The main causes of errors are offset drifts (<2 pV V K-1 per bridge). Inaccuracies due to form and uniaxial or crystal anisotropy are only in the range of... 

Therefore, GMR angle sensors have a natural 360° measuring range, in contrast to the 180° covered by AMR sensors. The angle signal calculated from the arctangent does not repeat after 180° as occurs with AMR sensors, so that no additional sensor or planar coils are necessary to sense a complete rotation of an external field. 

U. Caduff, H. Schweren, H. Kittel, Low cost angle sensors for multi-purpose applications, SAE Conference, Detroit, Michigan, March 6-9, 2000 ... 

Function Modeling of Steering-Angle Sensor Principles... 

Fig. 7.11.3 Contactless steering-angle sensors with active and fixed transmitter...

Fig. 7.11.8 Steering-angle sensor using Gray code technique [15]...

Fig. 7.11.9 Steering-angle sensor principle based on an optical array [9]...

Fig. 7.11.13 Steering-angle sensor principle as a separate optical sensor head (source Valeo)...

Fig. 7.11.19 True power on and absolute steering-angle sensor measuring principle (source Bosch)...

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