| 摘要 |
PURPOSE:To perform measurement even with respect to a largely varying detection signal, by successively changing the amplification degrees of amplifying circuits in the upstream side and the downstream side to different values and receiving each magnitude of signal in the tolerant range of a multiplier circuit. CONSTITUTION:When the amplitudes of upstream and downstream side detection signals 1a, 2a become large or the amplitude of the downstream side detection signal 2a varies abruptly, the amplification degree of an upstream side amplifying circuit 13 is automatically controlled by auxiliary comparators CM12, CM13 and a main comparator CM11 corresponding to said amplitudes or amplitude change and that of a downstream side amplifying circuit 14 is also automatically controlled by auxiliary comparators CM22, CM23 and a main comparator CM21 in the same way and the amplitudes of first and second signals 6a, 8a inputted to a multiplier circuit 9 are certainly and stably received in the tolerant input voltage range of the multiplier circuit 9 over a wide range of 1-16 times the reference amplitude X0 of the detection signals 1, 2. By this speedometer 23, well accurate measurement can be performed even if the amplitudes of the detection signals 1a, 2a largely vary.
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