# Ammeter

Demonstration model of a moving iron ammeter. As the current through the coil increases, the plunger is drawn further into the coil and the pointer deflects to the right.
Wire carrying current to be measured.
Spring providing restoring force
This illustration is conceptual; in a practical meter, the iron core is stationary, and front and rear spiral springs carry current to the coil, which is supported on a rectangular bobbin. Furthermore, the poles of the permanent magnet are arcs of a circle.
Ammeter from the old Penn Station Terminal Service Plant in New York City
Zero-center ammeter
An older moving iron ammeter with its characteristic non-linear scale and with the moving iron ammeter symbol mounted on a small form factor PC.

An ammeter (from Ampere Meter) is a measuring instrument used to measure the current in a circuit. Electric currents are measured in amperes (A), hence the name. Instruments used to measure smaller currents, in the milliampere or microampere range, are designated as milliammeters or microammeters. Early ammeters were laboratory instruments which relied on the Earth's magnetic field for operation. By the late 19th century, improved instruments were designed which could be mounted in any position and allowed accurate measurements in electric power systems. It is generally represented by letter 'A' in a circle. Ammeters have very low resistance and are always connected in series in any circuit.

## History

The relation between electric current, magnetic fields and physical forces was first noted by Hans Christian Ørsted who, in 1820, observed a compass needle was deflected from pointing North when a current flowed in an adjacent wire. The tangent galvanometer was used to measure currents using this effect, where the restoring force returning the pointer to the zero position was provided by the Earth's magnetic field. This made these instruments usable only when aligned with the Earth's field. Sensitivity of the instrument was increased by using additional turns of wire to multiply the effect – the instruments were called "multipliers".[1]

The word rheoscope as a detector of electrical currents was coined by Sir Charles Wheatstone about 1840 but is no longer used to describe electrical instruments. The word makeup is similar to that of rheostat (also coined by Wheatstone) which was a device used to adjust the current in a circuit. Rheostat is a historical term for a variable resistance, though unlike rheoscope may still be encountered.[2][3]

Other Languages
العربية: أميتر
azərbaycanca: Ampermetr
беларуская: Амперметр
български: Амперметър
català: Amperímetre
čeština: Ampérmetr
Cymraeg: Amedr
Ελληνικά: Αμπερόμετρο
español: Amperímetro
Esperanto: Ampermetro
euskara: Amperemetro
فارسی: آمپرسنج
français: Ampèremètre
galego: Amperímetro
한국어: 전류계
հայերեն: Ամպերմետր
हिन्दी: अमीटर
hrvatski: Ampermetar
Bahasa Indonesia: Amperemeter
isiXhosa: I-Ammeter
italiano: Amperometro
עברית: מד זרם
қазақша: Амперметр
Kiswahili: Ameta
Кыргызча: Амперметр
latviešu: Ampērmetrs
lietuvių: Ampermetras
македонски: Амперметар
മലയാളം: അമ്മീറ്റർ
မြန်မာဘာသာ: အမ်မီတာ
Nederlands: Stroommeter
नेपाली: एमिटर

norsk nynorsk: Amperemeter
oʻzbekcha/ўзбекча: Ampermetr
پنجابی: ایمیٹر
Piemontèis: Amperòmeter
polski: Amperomierz
português: Amperímetro
Qaraqalpaqsha: Ampermetr
română: Ampermetru
русский: Амперметр
Scots: Ammeter
shqip: Ampermetri
සිංහල: ඇමීටරය
Simple English: Ammeter
سنڌي: اميٽر
slovenščina: Ampermeter
српски / srpski: Амперметар
srpskohrvatski / српскохрватски: Ampermetar
Basa Sunda: Ampérméter
svenska: Amperemeter
తెలుగు: అమ్మీటరు
тоҷикӣ: Амперметр
Türkçe: Ampermetre
Türkmençe: Ampermetr
тыва дыл: Амперметр
українська: Амперметр
اردو: ایمیٹر
Tiếng Việt: Ampe kế