Electronic test pen distinguishes between alternating current and direct current
The first is to distinguish from the brightness. The brightness of the electric pen when measuring the alternating current is significantly higher than that of the direct current. The second is to distinguish from the position of the brightness of the electric pen. The light of the electric pen, called the neon tube, is in the shape of a long strip. When measuring alternating current, the entire neon tube glows; when measuring direct current, only one end of the neon tube glows.
