摘要 |
Pulse sequence (1) having rising pulses (2) of width (teven) and falling pulses (6) of width (todd) are output by a wheel speed measurement magnetic pole. Speed change is detected, when the conditions t(n+1) less than X /* t(n+3) and t(n+3) less than X /* t(n+1) are not satisfied, where X is the duty factor which is set preferably to 2. When the condition t(n+5) greater than X /* t(n+3) is satisfied, signal drop-out is detected. Measurement poles arranged at periphery of magnetic wheel, output a pulse sequence (1) having rising pulses and falling pulses. When falling pulse continues for more than specific period, signal drop-out is detected.
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