- Clamp-on amp meters (better known as clamp-on ammeters) measure electric conductors of electricity with a sensor in-between the jaws of the clamp. In some applications, electricians pass the test material through the probe (the space between the clamp jaws) without clamping the jaw onto the test material. When measuring voltage, for example, the clamp's jaw isn't attached to anything. Clamp-on amp meters are used in a number of applications by electricians, engineers and technicians. Some common uses for clamp sensors include: power plant maintenance and inspection; home electrical system maintenance/repair; and industrial manufacturing applications.
- The clamp-on amp meter is clipped to a wire within a circuit. The electrical current running through the wire generates an electromagnetic field around the wire. An amp meter reads the strength of the electromagnetic field via a sensor housed in the jaws of the clamp. The greater the electromagnetic field around the wire, the greater the current reading.
- To take a measurement with a clamp-on meter, close your hand around the clamp lever. Place the electrically conductive test material between the jaws. Carefully, release the clamp lever to close the jaws of the clamp sensor around the electrically conductive test material. When measuring the power in an electrical system, position the clamp so that the arrow indicator on the sensor is pointing to the load (loads are the connection points in an electrical system where things like appliances hook into). Use the rotary dial to toggle between types of measurement and units of measurement.
- Test the voltage in an electrical system by measuring the power side of the system and the load side. Set the rotary dial to V. Don't clamp the amp meter to anything for measuring voltage. Instead, use the voltage test leads (a pair of red and black wires connected to the clamp-on amp meter). Clip the red lead on the amp meter to the power supply in the electrical system. Clip the black lead to the load side of the electrical system. When measuring voltage, always connect the voltage leads to the test material/instrument before connecting the meter to an active electrical line. If you're testing electrical breakers, connect the clamp-on amp meter to the secondary side of the breaker. Never connect to the primary breaker, as electrical shock could result in death or injury.
- Test the current in an electrical system by measuring the power side of the system and the load side. Turn the rotary dial to A. Do not use the voltage leads for this test. Press the clamp lever to open the sensor jaws, and clamp the meter down on the test material.
