| 摘要 |
An optical system (5,8) is used to focus a light source (4) on to a moving thread (6) with its vibrations damped by a brake (7) to obtain an optical pattern (9) which is received by a photoelectric detector (10). The signal is scanned at fixed intervals and the length of each section during a scanning interval is measured. The overall length is given by the sum of all these lengths. The detector is followed by an amplifier (11) and a filter (12), the filtered signal passing to a zero pass circuit (13) and amplitude discriminator (14), to enter a period length measuring circuit (21). This has connections with a clock pulse generator (18) and a generator (19). A reciprocal value forming stage (22) establishes speed measuring values from the intervals. The lengths are passed to summing circuits (23,31) and the overall length is shown on an indicator (32). ADVANTAGE - High accuracy.
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