Rotary Position Sensor for High Speeds - The AS5132 magnetic rotary position sensor IC from ams is designed for high rotation speeds. With a propagation delay of less than 22µs and advanced pre-commutation, the device is designed to give angle measurement even in motors rotating at speeds up to 80,000rpm. Angle measurements are accurate to within ±3° (maximum). “BLDC motor manufacturers can achieve high and constant levels of torque even in high-speed applications over the whole dynamic range,” said the supplier. The chip combines Hall elements, an analogue front end and digital signal processing. It can dynamically compensate for angle errors attributable to propagation delay, which are most noticeable at high speeds ...

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Shukuji Asakura, Akimitsu Ishihara, Frequency Output Type Motion Sensor Using Self-excited Potential Oscillation, Sensors and Actuators, A 90, 2001, pp.111-117.

Abstract: A new method for measuring the velocity of a moving fluid around an electrode was proposed. The method measured the frequency of a self-excited oscillation of an iron electrode immersed in H3PO4-H2O2 solutions. The flow in the neighborhood of the electrode, on which transport processes depended, was presumed to change the oscillation frequency. The frequency is proportional to the concentration of the hydrogen peroxide, [H2O2], at the phosphoric acid concentration of 0.5 mol/dm3. The moving velocity of the electrode against the static solution could be determinated. In the same sense, the rotation speed of the electrode and the electrode tilt, which affected natural convection around an electrode, could be measured.

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Akimitsu Ishihara and Shukuji Asakura,  A Possible Motion Sensor with Frequency Output, In Proceedings of the 18th Chemical Sensor Symposium, April 3-5, 1994, Tohoku University, Japan, Vol.10, Supplement A.
Abstract - Electrochemical oscillations have often been observed in iron immersed in the solution containing phosphoric acid and hydrogen peroxide. This oscillation has been interpreted by the cross linkage between electrochemical reactions and mass transport processes in the vicinity of an electrode. Therefore, the oscillation frequency is expected to reflect the flow rate around the electrode. A rod of carbon steel S50C was mounted in rotating disc apparatus. The intersection of the rod rotated concentrically. In the mixture of 0.5M phospheric acid and 1.5M hydrogen peroxide the highly stable electrochemical oscillation appeared. The amplitude of potential change was about 600mVp-p. The oscillating frequency was a sensitive function of rotation rate in the range of 100 rpm to 2000. It is very possible to develop the motion sensors whose output is frequency by using this phenomenon.

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K.-M.H. Lenssen, D.J. Adelerhof, H.J. Gassen, A.E.T. Kuiper, G.H.J. Somers and J.B.A. van Zon, Robust Giant Magnetoresistance Sensors,  In Proceedings of the 13th European Conference on Solid-State Transducers (EUROSENSORS XIII), The Hague, The Netherlands, 12-15 September, 1999, pp.589-596.

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Winston Sun, Tao Mei, Antony W.-T. Ho, and Wen J. Li , A MEMS High-speed Rotation Measurement System with MCNC Fabricated Motion and Reference Sensors Using Wireless Transmission, in Proceedings of IEEE International Conference On Multisensor Fusion and Integration for Intelligent Systems (MFI 99’), Taipei, Taiwan, August 15-18, 1999