ROTATION DETECTING DEVICE FOR ROTATING BODY

摘要

PURPOSE:To generate rotation pulse signals with high accuracy and to enable accurate rotation detection by varying the bias input voltage of an amplifier so that the mean value becomes nearly constant and comparing this mean value with the level of a sensor signal. CONSTITUTION:The output signal of an MR sensor 2 is amplified 8 by using a reference voltage Vref as a bias voltage and the amplified signal Vfg is sup plied to a maximum holding means 9, a minimum holding means 10, and a comparator 12. Then the mean voltage Vave of the maximum voltage Vmax and the minimum voltage Vmin obtained by the means 9 and 10 is calculated 11 and supplied to a comparator 12 and a motor control means 15. The means 15 compares the voltage Vave with a reference voltage corresponding to the center voltage of a dynamic range and a reference voltage generating means 14 controls the level of the reference voltage Vref applied to the amplifier 8 according to the level of the mean value Vave of the sensor signal Vfg after amplification 8 so that the mean voltage Vave becomes constant. Then this voltage Vave is compared with the voltage Vfc after the amplification, so even if the output of the sensor 2 has slight AM variation, accurate rotation pulses are obtained.