| 摘要 |
1,125,511. Digital frequency measurement. HUGHES AIRCRAFT CO. 26 Aug., 1966 [13 Sept., 1965], No. 38418/66. Heading G4H. [Also in Division H3] An input sine wave is converted by a zero crossing detector 82 into pulses which are fed to a counter 84. At the start and stop of counter 84 a gate 88 is respectively opened and closed to allow clock pulses to pass from the source 86 to a second counter 85, which may re-cycle during the period determined by the counter 84. The residual count at the end of the period represents the frequency (or deviation from a predetermined frequency) and is converted into an analogue voltage by converter 62.
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