How to judge the output polarity of a DC welding machine: Regular welding machines are marked with + and-on the output terminal or wiring board, + means positive, and-means negative. If the positive and negative poles are not marked, the following methods can be used to distinguish. DC Welding Machine 1) Empirical method. When using a low-hydrogen type (or alkaline) electrode for welding, if the arc is unstable, spatters, and the sound is violent, it means that the forward connection method is used; otherwise, the reverse connection method is used. 2) Carbon rod method. When the carbon rod method is used to judge the forward connection or the reverse connection, it can also be judged by observing the arc and other conditions: a. If the arc combustion is stable and the carbon rod burns slowly, it is a positive connection method. b. If the arc combustion is unstable and the carbon rod burns severely, it is a reverse connection method. 3) Multimeter method. The method and steps for judgin...