Principle: Readings show the powerful voltage based upon the average price of samples in excess of a complete range of periods of the basic frequency trong m?t kho?n th?i gian nh?t ??nh tr??c khi ?i?u ch?nh, t?t nh?t b?n nên dùng ph??ng pháp t? ??ng ho?c xây d?ng hàm ?? ki?m tra v?i d? li?u.Ca?ch ?ô?i ve? tru?ng th???ng x? s? mi?n Nam an toa