3.1.1 the lower computer receives the upper computer detection start signal, switch the analog switch to the ground end. The adjustment W2 makes the A /D converter output zero or close to zero. after 3.1.2 zeroing, switch the analog switch to the sine wave signal output. According to the different frequencies of the predicted signal to be tested, the corresponding frequency sine wave is generated by the single chip microcomputer, and the output amplitude of the A /D converter is adjusted to reach the calibrated amplitude of the sine wave signal.