Verify there is no dc offset on the sinewave by momentarily setting the DVM to dc volts, and observing a reading of 0.000 V (the last two digits may fluctuate).

• 当瞬间设置DVM到直流电压档时，确认正弦波没有直流补偿，并观察0.；000V的读数（最后2位数字可能会变化）。