| 摘要 |
PURPOSE:To obtain an automatic voltage balance without a resistance trimming for manufacture of a detecting sensor of number of revolutions, by controlling balance of time widths of fluctuating pulse signals. CONSTITUTION:A magnetic sensor 1, in response to a magnetic field H rotating at a constant speed, generates a pulsating voltage V1, a overlapped voltage of DC voltage VD and AC voltage, and it is applied to a voltage comparator 2 as an input. Next, the comparator 2 generates a meter signal of a voltage H. And, a controlling unit 4, in response to this, increases a digital value of the controlling data and, in corresponding to this, a voltage V2 is increased also and when it plunges into a range between minimum and maximum values of the voltage V1, the meter signal repeats H and L voltages alternatively. Next, the controlling unit 4, as a duty ratio of the meter signal approaches 50%, controls the value of the controlling data in such a way that the duty ratio approaches 50%. By this arrangement, the duty ratio of meter signal converges actually into 50% and an automatic voltage balance can be obtained.
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