View source for Ammeter

[[Image:Amperemeter_hg.jpg|thumb|Ammeter]]
[[Image:Galvanometer diagram.png|thumb|right|250px|<font face="arial" color="red">Wire carrying current to be measured.</font><br><font face ="arial" color="green">Spring providing restoring force</font>]]
[[Image:Ammeter from New York Terminal Service Plant, 250 West Thirty-first Street 351263pv.jpg|thumb|right|Ammeter from the old [[Pennsylvania Station (New York City)|Penn Station]] Terminal Service Plant at 250 West Thirty-first Street]]
[[Image:Zero-Center_Ammeter.JPG|thumb|right|200px|Zero-center ammeter]]
{{SI}}



An '''ammeter''' is a [[measuring instrument]] used to measure the [[electric current]] in a [[Electrical circuit|circuit]]. Electric currents are measured in [[ampere]]s, hence the name. The word "ammeter" is commonly misspelled or mispronounced as "ampmeter" or "ameter" by some.

The earliest design is the [[Jacques-Arsène d'Arsonval|D'Arsonval]] [[galvanometer]] or moving coil ammeter. It uses [[magnetism|magnetic]] [[deflection]], where current passing through a coil causes the coil to move in a [[magnetic field]]. The [[voltage]] drop across the coil is kept to a minimum to minimize resistance across the ammeter in any circuit into which it is inserted.

Moving iron ammeters use a piece or pieces of [[iron]] which move when acted upon by the electromagnetic force of a fixed coil of (usually heavy [[Wire gauge|gauge]]) wire. This type of [[Meter (electronics)|meter]] responds to both [[direct current|direct]] and [[alternating current|alternating]] currents (as opposed to the moving coil ammeter, which works on [[direct current]] only).

To measure larger currents, a [[resistor]] called a [[shunt (electrical)#Use in current measuring|''shunt'']] is placed in [[Series and parallel circuits|parallel]] with the meter. Most of the current flows through the shunt, and only a small fraction flows through the meter. This allows the meter to measure large currents. Traditionally, the meter used with a shunt has a full-scale deflection (FSD) of {{nowrap|50 mV}}, so shunts are typically designed to produce a voltage drop of {{nowrap|50 mV}} when carrying their full rated current.

Zero-center ammeters are used for applications requiring current to be measured with both polarities, common in scientific and industrial equipment. [[Zero-center ammeters]] are also commonly placed in series with a [[battery (electricity)|battery]]. In this application, the charging of the battery deflects the needle to one side of the scale (commonly, the right side) and the discharging of the battery deflects the needle to the other side.

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.  

Since the ammeter shunt has a very low resistance, mistakenly wiring the ammeter in parallel with a voltage source will cause a [[short circuit]], at best blowing a fuse, possibly damaging the instrument and wiring, and exposing an observer to injury. In AC circuits, a [[Transformer#Current transformers|current transformer]] converts the magnetic field around a [[Electrical conductor|conductor]] into a small AC current, typically either 1 or 5 Amps at full rated current, that can be easily read by a meter. In a similar way, accurate AC/DC non-contact ammeters have been constructed using [[Hall effect]] magnetic field sensors. A portable hand-held [[clamp meter|clamp-on ammeter]] is a common tool for maintenance of industrial and commercial electrical equipment, which is temporarily clipped over a wire to measure current.  

== Ammeter Schematic Symbol ==
The ammeter symbol (A) is shown in the diagram.<br>[[Image:VoltmeterSymbol.jpg]]
==See also==
*[[Clamp meter]]
*[[Circuit diagram]]
*[[Electric circuit]]
*[[Electronic test equipment]]
*[[Electronics]]
*[[Galvanometer]]
*[[List of electronics topics]]
*[[Multimeter]]
*[[Ohmmeter]]
*[[Voltmeter]]




[[Category:Electronic test equipment]]
[[Category:Measuring instruments]]

[[ar:مقياس التيار الكهربائي]]
[[bg:Амперметър]]
[[ca:Amperímetre]]
[[cs:Ampérmetr]]
[[da:Amperemeter]]
[[de:Strommesser]]
[[el:Αμπερόμετρο]]
[[es:Amperímetro]]
[[eo:Ampermetro]]
[[fa:آمپرسنج]]
[[fr:Ampèremètre]]
[[gl:Amperímetro]]
[[it:Amperometro]]
[[he:מד זרם]]
[[lt:Ampermetras]]
[[hu:Villamos műszerek]]
[[nl:Ampèremeter]]
[[ja:電流計]]
[[pl:Amperomierz]]
[[pt:Amperímetro]]
[[ru:Амперметр]]
[[simple:Ammeter]]
[[sl:Ampermeter]]
[[fi:Ampeerimittari]]
[[sv:Amperemeter]]
[[vi:Ampe kế]]
[[tr:Ampermetre]]
[[uk:Амперметр]]
[[zh:电流表]]


{{WH}}
{{WS}}