| 摘要 |
PURPOSE:To compensate automatically an offset by a simple circuit constitution using an up-down counter. CONSTITUTION:In order to compensate automatically an offset, before an input Ex to be converted is A/D-converted, a contact piece of a changeover switch 50 is connected to a terminal 52 to make the input to an integrating device 10 to zero and to reset the up-down counter 70. When the integrating device 10 has an offset, a pulse width modulating signal is longer by the share of the offset and the counter 70 counts up a clock pulse fc during that time corresponding to the offset. The content of the counter 70 includes the offset of the integrating device 10. Then, the Ex enters the A/D conversion, the counter 70 counts down the clock pulse fc at first during the period of pulse width of the input Ex, and when the count value reaches zero, then the counter is counted up. The content of the counter 70 at the end of the said period becomes a digital signal corresponding to the Ex. |
