| 摘要 |
PROBLEM TO BE SOLVED: To perform accurately reset-to-zero determination by changing a threshold voltage corresponding to a driving voltage of a stepping motor, in reset-to-zero processing for determining that a pointer has reached a reset-to-zero position when an induced voltage of field winding is lower than the threshold voltage. SOLUTION: A reset-to-zero determination means 66 determines that the pointer 4 is returned to the zero (reference) position on the basis of an output from a voltage comparator 72 of an induced voltage detection circuit 7. A VDD supply voltage which is the driving voltage of the stepping motor 2 is detected by a voltage detection means 57. A threshold variable means 68 has a threshold table for storing a VDD supply voltage-versus-threshold characteristic, and calculates a threshold voltage corresponding to the VDD supply voltage on reference to the threshold table on the basis of the detected VDD supply voltage, and generates the calculated threshold voltage. The threshold voltage is supplied to a reference input terminal of the voltage comparator 72. COPYRIGHT: (C)2007,JPO&INPIT
|
