An ammeter is an instrument used to measure the flow of electric current in a circuit. It is typically connected in series with the circuit, allowing the current to pass through the ammeter for accurate measurement. Ammeters can display readings in various units, most commonly in amperes (A). There are different types of ammeters, including analog and digital models. Analog ammeters use a needle and dial to show current levels, while digital ammeters provide a numerical display. Both types are essential tools in electrical engineering and are used for troubleshooting and testing electrical systems.