Topic Ammeter Presenter: Hammad Ashfaq
Definition • An ammeter is an instrument that measures electric current, usually in units of amperes (or milliamps or micro amps when very small currents are involved). Both the magnitude of direct current (DC) and alternating current (AC) can be measured, though with ammeters of different types.
The earliest design of an ammeter • The earliest design of an ammeter was invented by a french guy called D'Arsonval in 1882. • It was called galvanometer and was a mechanical device
Basic types of Ammeter • There are two basic types of ammeters. • 1. The moving coil ammeter • 2. The moving iron or moving magnet ammeter
Principles of Ammeter • Both versions use a principle discovered by Hans Christian Oersted in 1820, which holds that an electric current in a wire produces a magnetic field. • The magnetic field exerts a force on a coil, making it turn. • A pointer that is attached to the coil or magnet also moves, allowing the measurement to be read off the scale.
Principles of Ammeter • The moving coil ammeter has three basic parts: a permanent magnet, a coil, and a coil spring.
Principles of Ammeter • When current is passed through the coil it creates a magnetic field that is opposite that of the permanent magnet, causing the coil, and its attached pointer, to pivot. • The coil spring not only limits the distance the coil can rotate, but the amount of tension it exerts depends on the strength of the force turning the coil.
Working of An Ammeter • An ammeter is placed in series with a circuit element to measure the electric current flow through it. • The meter must be designed offer very little resistance to the current so that it does not appreciably change the circuit it is measuring.
Working of An Ammeter • A small resistor is placed in parallel with the galvanometer to shunt most of the current around the galvanometer. • Its value is chosen so that when the design current flows through the meter it will deflect to its full-scale reading.
Working of An Ammeter • Digital ammeter designs use an analog to digital converter (ADC) to measure the voltage across the shunt resistor. • The digital display is calibrated to read the current through the shunt.
Modern Working System Digital displays are extremely accurate and easy to operate, but they are more expensive than their electro-mechanical cousins.
Uses • Sometimes referred to as an ammeter, the ammeter can be utilized in a number of different fields. • The device is handy for measuring the flow of current through the wiring systems of new buildings, ensuring the wiring is up to acceptable local safety codes.
Uses • Electricians will often make use of an ammeter to spot problems with wiring systems in older buildings. • Circuit breaker with integrated ammeter • In general, the ammeter can be utilized in just about any situation where it is possible to tap into a circuit and execute a measurement.
Uses • Companies that manufacture electrical equipment of just about any kind will make use of an ammeter in testingthe products before offering them for sale.
Advantages • We can measure the current more accurate in the circuit. • No ganger of shock by measuring current.