Power tools are tools that require electricity, usually 230 volts, to operate. Battery-operated (cordless) power tools are becoming increasingly popular, especially among amateur DIYers. The most common power tools are drills, screwdrivers, chainsaws, jigsaws, hammers, grinders, planers, routers, air compressors, and welders. Testers are instruments that, by means of a display or an analog scale and pointer, allow reading the magnitude measured. One of the most popular testers used in electrical engineering/electronics is the digital multimeter, which facilitates measurement DC and AC voltage and current, as well as electrical resistance of circuits.