| 摘要 |
PURPOSE:To enable accurate display below a second, by driving a step motor by counting a 20Hz signal by a vigesimal counter to display time below a second by a 1/20 second hand. CONSTITUTION:When an start stop signal St reaches a high level corresponding to a switch 3, a 20Hz pulse phi20 is outputted from a 20Hz signal forming circuit 8 to start the calibration due to a vigesimal counter 9 while a motor drive circuit 13 selects the pulse phi20 as a drive pulse phiM to drive a step motor 16 and a calibration time below a second is displayed by a 1/20 second hand 18. On the other hand, when a switch 4 is closed after the switch 3 is opened, the 20Hz signal is cut off while the counter 9 is reset to reverse the output of a coincidence detecting circuit 11 to a low level and the circuit 13 selects a 16Hz signal phi16 from a frequency dividing circuit 12 to restore the hand 18 to a zero position. The display of an intermediate time is similarily carried out and the time below a second is displayed by a hand through a proper display unit propperly and accurately. |
