A current tester is a device that measures the magnitude and direction of electrical current and monitors the efficiency and performance of a power system. They help isolate electrical leakage and locate insulation breakdowns on live circuits. An electric current tester measures by mechanical, acoustical, or electrical means. Devices such as ammeters, clamp meters, current clamps, and current probes are different types of current testers. An ammeter is a current tester that measures electrical current in automotive applications. Sometimes called a clamp-on meter, a clamp meter measures electrical current without touching or interrupting the circuit. Current clamps and current probes are attachments for electrical testing devices that measure current. A clamp typically has two jaws that encircle a conductor without touching it. Other types of clamps and probes attach to an object, such as a metallic pipe or a cable, to detect and measure current. Current testers are commonly used for installing and maintaining industrial, commercial, and residential power systems.