amperimeters

An ammeter is an electrical instrument used to measure the electric current in a circuit. It is designed to be placed in series with the circuit element whose current is to be measured, so that the entire current flows through the ammeter. Ammeters are typically characterized by their low internal resistance, which is crucial for accurate measurement. If an ammeter had a high resistance, it would significantly alter the current it is intended to measure.

The unit of electric current is the ampere, often denoted by the symbol 'A'. Ammeters are calibrated to display this measurement directly. Historically, ammeters were electromechanical devices, often employing a galvanometer. A galvanometer is a sensitive instrument that detects and indicates small electric currents. In a typical electromechanical ammeter, a coil carrying the current to be measured is placed in a magnetic field. The interaction between the magnetic field and the current produces a torque that deflects a pointer across a calibrated scale.

Modern ammeters are often digital. These instruments use electronic components to measure the current. Digital ammeters typically convert the current into a voltage, which is then processed by an analog-to-digital converter (ADC). The resulting digital value is displayed on a screen, often a liquid crystal display (LCD). Digital ammeters offer advantages such as higher precision, easier reading, and the ability to incorporate additional features like data logging.

When using an ammeter, it is essential to connect it correctly in series. Reversing the polarity can lead to incorrect readings or damage to the instrument, especially with DC ammeters. Different types of ammeters exist, including DC ammeters for direct current and AC ammeters for alternating current. AC ammeters may employ different principles of operation, such as using transformers to reduce the current before measurement.