AD CONVERSION SYSTEM

PURPOSE:To attain AD conversion without offset by using a digital signal processing section so as to detect the offset and to correct it based on an input signal during a period of no input to the AD converter and an output signal of the AD converter of the period. CONSTITUTION:The AD converter applies the 1st conversion at a time t=1, and an analog signal V1 is converted into a digital signal C1 in this case. Then the 2nd conversion is applied at a time t=2 and an analog signal V2 in converted into a digital signal C2. The cycle above is repeated at t=m, that is, at the end of offset detecting period. When the offset detection period is finished at t=m, an offset is calculated and detected in a digital signal processing section. Then offset correction AD conversion is started based on the detected offset and the processing is continued till the signal processing system reaches the state of the end of AD conversion. Thus, the AD conversion independently of the offset of the AD converter is attained.