| 摘要 |
PURPOSE:To make it possible to confirm whether DC voltage to be measured is a prescribed voltage, by normalizing the difference of the polarity of DC voltage to be measured by an operational amplifier and a resistor to read the same as digital data. CONSTITUTION:When the nominal voltage value of DC input voltage E1 is inputted, resistors R1, R2 are selected so that the output voltage Ex1 of an operational amplifier 1 becomes a constant value to normalize voltage E1. Similarly, the input voltage -E2 of the operational amplifier 2 is also normalized. An AD converter 3 outputs the digital data Dx1 corresponding to the normalized output voltage Ex1 on the basis of the chip selection signal 100 and reading signal 102 from a digital data reading circuit 5. Similarly, an AD converter 4 outputs digital data Dx2. Therefore, in both positive and negative cases of DC input voltage, when voltage of which value is alpha-times the nominal voltage value is inputted, a value alpha-times the digital data corresponding to the nominal voltage value is outputted as the output digital data of the converter 3 or 4. That is, regardless of the magnitude of the polarity or voltage absolute value of DC voltage, the ratio to the nominal voltage value can be judged from the digital data value by the circuit 5 and it can be confirmed whether voltage to be measured has a prescribed voltage value.
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