PURPOSE: To minimize the distortion output by adding a storage start control circuit between an A/D converter storage circuit and a storage start signal generating source and coupling a storage set signal generating source to the A/D converter storage circuit.
CONSTITUTION: When a digital value is inputted through a bias digital signal source 2, it is converted into an analog signal at a D/A converter 4, the converted signal is superimposed on a signal inputted from a measuring reference signal source 1 at an input circuit 5, and the result is inputted to an analog signal delay device 6. The distortion output is extracted from the analog signal delay device 6 and converted into a DC voltage at an output conversion circuit 7, the DC voltage is converted into a digital value at an A/D converter 8 by the signal of an A/D conversion start signal generation source 9, it is compared as the distortion output with a preceding signal stored in an A/D conversion storage circuit 10 at a comparator circuit 12 and also inputted to the A/D conversion storage circuit 10, the preceding signal is cancelled by a signal from the storage set generating source 14 and the distortion output is stored therein.
HIRAKAWA KENJI
USUI SHIYUNICHI
