| 摘要 |
PURPOSE:To reduce an error in measurement caused when a frequency tracking unit is incapable of tracking, by inputting to a pulse counter the output of a V-F transducer which is held in and output to an output frequency of a frequency divider just before the lock-off of the frequency tracking unit. CONSTITUTION:When a frequency tracking unit 9 is in the lock-off state, a latch circuit is put in a latching state by a lock-off signal of a lock-on detector 18. Therefore an F-V transducer 15a outputs, in a holding manner, an analog voltage being proportional to an output frequency of a frequency divider 10 just before the lock-off of the tracking unit 9. Accordingly, the output of a V-F transducer 17 is signal obtained by holding a frequency equal to the output frequency of the frequency divider 10 just before the lock-off. The output pulse of the frequency divider 10 and the output pulse of the transducer 17 are switched over by a lock-on signal of the detector 18 so that the former be used on the occasion of lock-on and the latter on the occasion of lock-off as a length measurement pulse respectively, and thereby an error in measurement occurring on the occasion of lock-off can be reduced. Since the moving speed V of an object 1 does not change sharply, the error is with in a negligible measurement scope in regard to the lock-off in a short time.
|
