vooluallika klemmipinge ja voolutugevuse vaheline sõltuvus keevituse vooluahelas; eristatakse püsivpingega (jäiga tunnusjoonega) ja püsivvooluga (järsult langeva tunnusjoonega) vooluallikaid (vt püsivpingega vooluallikas; püsivvooluga vooluallikas), a relationship, typically represented as a graph, between the electric current through a circuit, device or material during welding, and the corresponding voltage, or potential difference, across it; typical welding power sources characterized by different volt-ampere characteristics are constant-current source and constant-voltage source (see: constant-current power source; constant-voltage power source)