| 摘要 |
PURPOSE:To detect even low voltages which are lower than the threshold level of a comparator, by detecting and displaying that a supply voltage is lower than the lowest operating voltage of the comparator. CONSTITUTION:The value of a constant-voltage diode 6 is set in such a way that the value of the voltage across the (+)-side input and (-)-side input of a comparator 5 becomes equal to the lowest operating voltage of a supply voltage. Therefore, when the supply voltage is lower than the lowest operating voltage, a display device 10 lights and informs an operator of the abnormal supply voltage. In the same way, by setting the value of another constant-voltage diode 13 to a prescribed value, another display device 15 lights when the supply voltage is higher than the highest operating voltage. On the other hand, since the set voltage of a constant-voltage diode 3 connected with a resistance 1 and display device 2 is higher than the operable voltage of the comparator 5, the display device 2 does not light when the supply voltage is ''0''V or lower than the operating voltage of the comparator 5.
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