Principle: Readings exhibit the helpful voltage determined by the average price of samples around an entire variety of periods of the elemental 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.Just set a threshold on a meter looking at or sc