| 摘要 |
PROBLEM TO BE SOLVED: To highly reliably monitor normality/abnormality in A/D conversion in simplified, miniaturized and inexpensive configuration. SOLUTION: This A/D converter is provided with an operational amplifier 25 for amplitude correction provided on the prestage of a sample/hold circuit 29 to be operated by a positive or negative single power source for supplying an AC input signal SI to one input terminal, a DC bias power source for applying the bias voltage of the 1/2 power supply voltage of the amplifier 25 to the other input terminal of the amplifier 25 and correcting the signal SI so as to change the amplitude with the bias voltage as a center and a state monitoring part for monitoring and detecting normality/abnormality in A/D conversion by finding the measured data of the bias voltage from the average of signals SI in digital data outputted from an A/D converting part 30 for one cycle and discriminating whether a difference between these data and the set reference data of the bias voltage is settled within a prescribed error range or not. |
