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Electric current

currentcurrentselectrical current
An ammeter (from Ampere Meter) is a measuring instrument used to measure the current in a circuit.
Electric current is measured using a device called an ammeter.

Measuring instrument

instrumentscientific instrumentinstruments
An ammeter (from Ampere Meter) is a measuring instrument used to measure the current in a circuit.
Ammeter

Galvanometer

tangent galvanometernull detectorgalvanoscope
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.
Early galvanometers were not calibrated, but their later developments were used as measuring instruments, called ammeters, to measure the current flowing through an electric circuit.

Edward Weston (chemist)

Edward WestonDr. Edward WestonWeston
The modern form of this instrument was developed by Edward Weston, and uses two spiral springs to provide the restoring force.
Weston developed measurement instruments for electric current—the modern foundation for the voltmeter, ammeter and wattmeter.

Multimeter

digital multimeterdigital multimetersmultitester
Picoammeters are used for sensitive measurements where the current being measured is below the theoretical limits of sensitivity of other devices, such as Multimeters.
Analog multimeters use a microammeter with a moving pointer to display readings.

Voltmeter

Digital voltmetervolt metervoltmeters
This type of meter movement is extremely common for both ammeters and other meters derived from them, such as voltmeters and ohmmeters.
Ammeter

Wattmeter

electrodynamometerMirror bifilar electrodynamometerpower meter
See Wattmeter for an alternative use for this instrument.
Here, cosφ represents the power factor which shows that the power transmitted may be less than the apparent power obtained by multiplying the readings of a voltmeter and ammeter in the same circuit.

Ohmmeter

measuredtwo-terminal (2T) sensing
This type of meter movement is extremely common for both ammeters and other meters derived from them, such as voltmeters and ohmmeters.
Ammeter

Ampere

AmAamp
Electric currents are measured in amperes (A), hence the name.
Ammeter

Shunt (electrical)

shuntshuntsparallel shunt connections
Digital ammeter designs use a shunt resistor to produce a calibrated voltage proportional to the current flowing.
An ammeter shunt allows the measurement of current values too large to be directly measured by a particular ammeter.

Class of accuracy in electrical measurements

Class of accuracy in electrical measurements
In electrical engineering characteristics like current or voltage can be measured by an ammeter, a voltmeter, a multimeter, etc. The ammeter is used in series with the load, so the same current flows through the load and the ammeter.

William Edward Ayrton

Ayrton, William EdwardProfessor AyrtonProfessor William Edward Ayrton
A better arrangement is the Ayrton shunt or universal shunt, invented by William E. Ayrton, which does not require a make-before-break switch.
He published, both alone and jointly with others, a large number of papers on physical, and in particular electrical, subjects, and his name was especially associated, together with that of Professor John Perry, with the invention of a long series of electrical measuring instruments, including the spiral-spring ammeter, and the wattmeter.

Current transformer

CTsTransformer
In AC circuits, a current transformer converts the magnetic field around a conductor into a small AC current, typically either 1 A or 5 A at full rated current, that can be easily read by a meter.
For current measurement, phase shift is immaterial as ammeters only display the magnitude of the current.

Ayrton shunt

A better arrangement is the Ayrton shunt or universal shunt, invented by William E. Ayrton, which does not require a make-before-break switch.
Multirange ammeters that use this technique are more accurate than those using a make-before-break switch.

Electric power system

power systempower systemsenergy systems
By the late 19th century, improved instruments were designed which could be mounted in any position and allowed accurate measurements in electric power systems.

Hans Christian Ørsted

ØrstedHans Christian OerstedH.C. Ørsted Lectureship
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.

Compass

magnetic compassDigital compassmariner's compass
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.

Charles Wheatstone

WheatstoneSir Charles Wheatstonepolar clock
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.

Potentiometer

rheostatpotentiometersvariable resistor
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.

Magnetism

magneticmagneticsmagnetically
It uses magnetic deflection, where current passing through a coil placed in the magnetic field of a permanent magnet causes the coil to move.

Deflection (engineering)

deflectiondeflectionsdeflect
It uses magnetic deflection, where current passing through a coil placed in the magnetic field of a permanent magnet causes the coil to move.

Magnetic field

magnetic fieldsmagneticmagnetic flux density
It uses magnetic deflection, where current passing through a coil placed in the magnetic field of a permanent magnet causes the coil to move.

True RMS converter

RMS converterstrue RMS
This instrument can respond to both alternating and direct current and also indicates true RMS for AC.

Iron

FeFe 2+ Fe(III)
Moving iron ammeters use a piece of iron which moves when acted upon by the electromagnetic force of a fixed coil of wire.