| 摘要 |
PURPOSE:To improve a precision even for a unipolar input, by superposing the half of a voltage corresponding to the full scale of the unipolar analogue signal onto the input voltage and reducing the A/D conversion gain to the half when a bipolar analogue signal input is selected. CONSTITUTION:In case of a unipolar input, an analogue switch 21 is switched to the U side, and an analogue switch 22 is turned off. When the input is subjected to D/A conversion under this state, a D/A converter 13 is 0V and an output register 19 is 00-00 when the input is 0V. The converter 13 is V/2 and the register is 10-0 when the input is V/2, and the converter 13 is V and the register 19 is 11- 11 when the input is V. In case of a bipolar input, the switch 21 is switched to the B side, and the switch 22 is turned on. Consequently, the conversion gain becomes V/2, and V/2 is offset. |
