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current_sensor [2019/06/03 18:29]
current_sensor [2020/07/19 00:06] (current)
stan_zurek
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 +====== Current sensor ======
  
 +|< 100% >|
 +| //[[user/Stan Zurek]], Current sensor, [[http://Encyclopedia-Magnetica.com|Encyclopedia-Magnetica.com]], {accessed @YEAR@-@MONTH@-@DAY@}// |
 +| //[[/wiki/reviewed]] by [[user/Jeanete Leicht]], 2013-04-04// |
 +
 +===== Definition =====
 +
 +**Current sensor**[(Telcon>[[http://www.telcon.co.uk/PDF%20Files/HESQ50_100.pdf|Miniature Electronicless Closed Loop Current Transformer HESQ50 & HESQ100, Telcon, {accessed 19 Feb 2013}]])], **current transducer**[(Lem>[[http://www.lem.com/docs/products/hlsr-p%20series.pdf|Current Transducer HLSR-P series, LEM, {accessed 19 Feb 2013}]])] or **current probe**[(Fluke>[[http://assets.fluke.com/manuals/80i400__iseng0600.pdf|Instruction sheet, 80i-400, AC Current Probe, Fluke, {accessed 19 Feb 2013}]])] - any type of sensor or transducer used for measurement or detection of [[electrical current]].
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 +[[Open-loop sensing technique]] with a [[Hall-effect sensor]]
 +[[file/open_loop_current_sensor_magnetica.png|{{open_loop_current_sensor_magnetica.png}}]]
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 +A current sensor provides means of converting the input signal to a different level or different physical quantity. There are a number of physical phenomena which can be employed for current sensing. Many of them involve various means of [[magnetic coupling]], but there are several in which [[magnetism]] does not play significant role.
 +
 +The output signal of a current sensor is typically voltage (as in a [[shunt resistor]]) or current (as in a [[current transformer]]). 
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 +
 +===== Examples of current sensors =====
 +
 +An example of the simplest current sensor is a [[non-inductive resistor]] which is inserted directly into the path of the current to be detected. The [[voltage drop]] across such resistor is directly proportional to the current flowing through it, so there is a conversion from current to voltage (which is generally easier to measure. The major disadvantage is lack of [[galvanic separation]][([[http://google.com/books?isbn=9780203961834|Slawomir Tumanski, Principles of electrical measurement, CRC Press, 2006, ISBN 9780203961834, p. 147]])], but also heat dissipation.[(Sensors_B>[[http://google.com/books?isbn=8073001292|Ripka P., Tipek A. (editors), Master Book on Sensors, Part B, BEN, ISBN 80-7300-129-2, p. 10-76, 10-77]])]
 +
 +Many current sensors are based on magnetic coupling, in which a significant place is held by [[current transformer|current transformers]], which electromagnetically transform the amplitude of the primary current into secondary current of usually different amplitude. They can offer full galvanic separation, but without special circuits they are unable to detect the [[DC component]] of the current. This is an inherent problem of all current probes based only on the effect of [[magnetic induction]].
 +
 +There is another class of sensors detecting [[magnetic field]] generated the current, and hence the value of the current. The magnetic field is guided by a [[magnetic core]], but the actual detection is achieved not by induction coil, but by a [[Hall-effect sensor|Hall-effect]], [[fluxgate sensor|fluxgate]], [[magnetoresistive sensor|magnetoresistive]], and so on.[([[http://google.com/books?isbn=9780471394846|Stephen A. Dyer (editor), Wiley Survey of Instrumentation and Measurement, Wiley-Interscience, John Wiley & Sons, 2001, ISBN 978-0471394846, p. 65]])] The construction of such sensors is more complex, but they are capable of detecting AC as well as DC components. They are sometimes referred to as [[DC current transformer|DC current transformers]].[(Sensors_B)]
 +
 +[[Faraday effect]] is also used in some modern applications. They can offer a high degree of galvanic isolation required for instance in high-voltage applications.[(Sensors_B)][(Guillermo Robles, Romano Giannetti, Magneto-optic Faraday effect current sensor based on thin cobalt films, Proceedings of the 17th [[IEEE]] Instrumentation and Measurement Technology Conference (IMCT), 2000)]
 +
 +There numerous other effects and phenomena which can be used for current sensing, without and with electrical isolation. Some of these are more popular than others and the exact implementation depends very strongly on the level of current to be measured, frequency of operation, required accuracy, etc. Most of these are at various degrees of research or development and might not be always available commercially. 
 +
 +Vast majority of presently available industrial sensors are still based on magnetic effects.
 +[([[http://www02.abb.com/global/atabb/atabb104.nsf/0/4b9d658ae545650dc1257475002cd988/$file/Elektronische_Strom_Spannungswandler.pdf|Current Sensors, Voltage Sensors, Technical Catalogue, ABB, France, {accessed 19 Feb 2013}]])] And even shunt resistors are best to be non-inductive, as [[parasitic inductance]] causes additional voltage drop (hence errors) at elevated frequencies.[([[http://google.com/books?isbn=9780471394846|Stephen A. Dyer (editor), Wiley Survey of Instrumentation and Measurement, Wiley-Interscience, John Wiley & Sons, 2001, ISBN 978-0471394846, p. 255]])]
 +
 +
 +===== Photos and images =====
 +
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 +Electronic [[current transformer]] converts the [[primary current]] to a different level of [[secondary current]]
 +[[file/epcos_smt_current_sense_transformer_magnetica.jpg|{{epcos_smt_current_sense_transformer_magnetica.jpg}}]]
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 +Thick-film [[non-inductive resistor]] can be used as a [[shunt resistor]] and convert current to voltage
 +[[file/thick-film_non-inductive_resistor_magnetica.jpg|{{thick-film_non-inductive_resistor_magnetica.jpg}}]]
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 +Clamp-on current transducers
 +[[file/clamp_current_meters_magnetica.jpg|{{clamp_current_meters_magnetica.jpg}}]]
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 +</box>
 +
 +
 +===== Examples of current sensors and transducers =====
 +  * [[Shunt resistor]]
 +  * [[Current transformer]]
 +  * [[Differential current transformer]]
 +  * [[AC current transformer]]
 +  * [[DC current transformer]]
 +  * [[Hall-effect current sensor]] (open loop and closed loop)
 +  * [[Fluxgate current sensor]]
 +  * [[Quadrature current transformer]]
 +  * [[Rogowski coil]]
 +  * [[Residual current detector]]
 +  * [[Faraday-effect current sensor]]
 +
 +===== References =====
 +~~REFNOTES~~
 +
 +{{tag>Sensors Transducers Counter}}

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