WILMSHURST, T.H., ROTHBERG, S. and HALLIWELL, N.A., 1991. Laser torquemeter -immunity to memory quantization noise. Electronics Letters, 27 (22), pp. 2037 - 2038.
Operation of the laser torquemeter relies on the periodicity of the speckle pattern backscattered from a rotating shaft. In the previous system a minimum measurable twist of 0.7' was imposed by address quantisation of the stored speckle pattern signals. The arrangement described provides immunity to this quantisation and the associated limit cycle oscillation, reducing the noise spectrum level to 3"/Hz12/ RMS while allowing 100 time-resolved torque readings per rotation.
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The work is supported by the Paul Instrument Fund of The Royal Society.