| 摘要 |
PURPOSE:To prevent the measurement of low reliability or malfunctioning by forming a reference pulse with a pulse width equivalent to a fine time interval at the measurable minimum or near it synchronizing the leading edge of a first pulse signal with a time interval measuring circuit to generate an alarm when there is the leading of a second pulse or a signal equivalent to the leading edge thereof during the period of the reference pulse. CONSTITUTION:A second AND circuit 15 functioning as discrimination circuit transmits an AND output between an output of an AND circuit 14 at the front stage and a second pulse signal comprising a square wave pulse train supplied from the second signal line 2. As illustrated by t4-t5 or t7-t8, when the time TX to be measured is small, there is a period during which a reference pulse and the second pulse are generated simultaneously to obtain a discrimination output for indicating the disability or caution of measurement as illustrated by E. In response to an output of the AND circuit 15 for discrimination, an alarm circuit 16 forms a signal as illustrated by F with a trigger monostable mjltivibrator 17 set at an output pulse width T. Based on this signal, an oscillation circuit 18 is driven to form a constant frequency signal as illustrated by G and a signal as shown by G is amplified with a driving circuit 19 to be fed to a light emitting element 20. Thus, an alarm is generated with the flashing of the light emitting element 20. |
