Editing Hall effect sensor (section)

=== Ammeters ===
Hall sensors may be utilized for contactless measurements of [[direct current]] in [[current transformer]]s. In such a case the Hall sensor is mounted in a gap in the magnetic core around the current conductor.<ref>{{cite book |last1=Petruk |first1=O. |title=Digitally Controlled Current Transformer with Hall Sensor |last2=Szewczyk |first2=R. |last3=Salach |first3=J. |last4=Nowicki |first4=M. |date=2014 |publisher=Springer |isbn=978-3-319-05352-3 |series=Advances in Intelligent Systems and Computing |volume=267 |pages=641 |doi=10.1007/978-3-319-05353-0_61}}</ref> As a result, the DC [[magnetic flux]] can be measured, and the DC in the conductor can be calculated.

[[File:HallEffCurrentSense.jpg|right|thumb|250x250px|Hall effect current sensor with internal integrated circuit amplifier. 8 mm opening. Zero current output voltage is midway between the supply voltages that maintain a 4 to 8-volt differential. The non-zero current response is proportional to the voltage supplied and is linear to 60 amperes for this particular (25&nbsp;A) device.]]

When electrons flow through a conductor, a magnetic field is produced. Thus, it is possible to create a non-contacting [[current sensor]] or [[ammeters]]. The device has three terminals. A sensor voltage is applied across two terminals and the third provides a voltage proportional to the current being sensed. This has several advantages; no additional resistance (a [[Shunt (electrical)|''shunt'']], required for the most common current sensing method) needs to be inserted in the primary circuit. Also, the voltage present on the line to be sensed is not transmitted to the sensor, which enhances the safety of measuring equipment.[[File:RAZC-GENARRv1.jpg|left|thumb|Diagram of Hall effect current [[transducer]] integrated into ferrite ring]]
[[File:Ampere-Turnsv1.jpg|thumb|Multiple 'turns' and corresponding transfer function]]

==== Improving signal-to-noise ====
Integrating a Hall sensor into a ferrite ring (as shown) concentrates the flux density of the current's magnetic field along the ferrite ring and through the sensor (because flux flows through ferrite much better than through air),<ref name=":0"/> which greatly reduces the relative influence of stray fields by a factor of 100 or better. This configuration also provides an improvement in [[signal-to-noise ratio]] and drift effects of over 20 times that of a bare Hall device.

The range of a given feedthrough sensor may also be extended upward and downward by appropriate wiring. To extend the range to lower currents, multiple turns of the current-carrying wire may be made through the opening, each turn adding to the sensor output the same quantity; when the sensor is installed onto a printed circuit board, the turns can be carried out by a staple on the board. To extend the range to higher currents, a current divider may be used. The divider splits the current across two wires of differing widths and the thinner wire, carrying a smaller proportion of the total current, passes through the sensor.

==== Current clamp ====
{{Main article|Current clamp}}
A variation on the ring sensor uses a [[Current clamp#Hall effect|split sensor]] which is clamped onto the line enabling the device to be used in temporary test equipment. If used in a permanent installation, a split sensor allows the electric current to be tested without dismantling the existing circuit.

The output is proportional to both the applied magnetic field and the applied sensor voltage. If the magnetic field is applied by a solenoid, the sensor output is proportional to the product of the current through the solenoid and the sensor voltage. As most applications requiring computation are now performed by small [[Computer|digital computers]], the remaining useful application is in power sensing, which combines current sensing with voltage sensing in a single Hall effect device.

By sensing the current provided to a load and using the device's applied voltage as a sensor voltage it is possible to determine the power dissipated by a device to form a [[wattmeter]].