Analog ammeters are metered instruments that measure current flow in amperes. They display current levels on a dial, usually with a moving pointer or needle. Analog ammeters provide information about current draw and current continuity in order to help users troubleshoot erratic loads and trends. They have both positive and negative leads and feature extremely low internal resistance. Ammeters are connected in series with a circuit (and never parallel) so that current flow passes through the meter. High current flow may indicate a short circuit, unintentional ground, or defective component. Low current flow may indicate high resistance or poor current flow within the circuit.
Analog ammeters can measure levels of alternating current (AC) and direct current (DC). Some devices that measure AC current also measure root mean square (RMS) power, which is the square root of the time average of the square of the instantaneous power. Many analog ammeters include a current sensor built into the meter or that clamps around the wire. Different types of analog ammeters can measure different ranges of AC current, DC current, and AC current frequency. Some devices are handheld and portable, while others are designed for benchtop or shop floor use. Battery-powered analog ammeters can be operated without plug-in power and are often suitable for outdoor use.
Optional features are available with many analog ammeters. Some devices can test the operation of batteries or diodes. Others include programming or components designed to counteract known errors caused by temperature changes. Mirrored scales make it easier to read analog ammeters to a given accuracy by enabling operators to avoid parallax errors. Analog ammeters carry a maximum rating and are used in a variety of applications and industries. Underwriters Laboratories (UL), the Canadian Standards Association (CSA) and other organizations certify many of the analog ammeters available today.