![\"Maxwell](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/maxwell-bridge.jpg\")
<\/p>\nMaxwell\u2019s Inductance Bridge measures an inductance by comparison with a variable standard self inductance. The bridge circuit arrangement with the phasor diagram are shown below in figure.<\/p>\n
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Under balance condition:<\/strong><\/p>\n Permanent Magnet Moving Coil (PMMC) Instrument<\/strong><\/p>\n The constructional features of PMMC instrument are shown below in figure which is very much similar to d\u2019Arsonval type of galvanometer. Equation of Torque:<\/strong><\/p>\n Let<\/p>\n d = width of the core Remember:<\/strong><\/p>\n Disadvantage of PMMC Instruments<\/strong><\/p>\n \u2022 The magnetic field produced is affected by the surrounding temperature which causes error in reading. Enhancement of PMMC Meters<\/strong><\/p>\n For reading higher range of current and voltage, Ammeter shunts and voltmeter multiplier are used respectively.<\/p>\n Ammeter Shunts<\/strong><\/p>\n When high current is to be measured, most of the current is bypassed through a low resistance called a \u201cshunt\u201d.<\/p>\n Effect of Temperature Changes in Ammeters<\/strong><\/p>\n If the surrounding temperature increases then, the meter resistance, Rm<\/sub> increases which causes decrease in the current through meter (Im<\/sub>) so that the meter reads errorneous value.<\/p>\n To compensate the temperature effect a resistance called \u201cswamp resistance\u201d is added in series with the meter. The swamp resistance is made up of mangnin which has low value of temperature coefficient.<\/p>\n The shunt resistance after addition of swamp resistance is given by<\/p>\n Multi-range Ammeter<\/strong><\/p>\n The current range of a d.c. ammeter can be extended by a number of shunts, selected by a range switch. <\/p>\n << Previous<\/a> | Next >><\/a> <\/p>\n","protected":false},"excerpt":{"rendered":" Maxwell\u2019s Inductance Bridge measures an inductance by comparison with a variable standard self inductance. The bridge circuit arrangement with the<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[389,5],"tags":[396,395,397,394],"class_list":["post-1294","post","type-post","status-publish","format-standard","hentry","category-electrical-electronic-measurements","category-ee","tag-ammeter-shunts","tag-deflecting-torque","tag-multi-range-ammeter","tag-permanent-magnet-moving"],"_links":{"self":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/1294","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/comments?post=1294"}],"version-history":[{"count":0,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/1294\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/media?parent=1294"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/categories?post=1294"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/tags?post=1294"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"Imaginary\"](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/imaginary.jpg\")
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\n\u2022 Principle of operation:<\/strong> The moving coil consists of number of turns of fine wire and current is passed through it. The iron core provides a flux path of low reluctance which creates a strong magnetic field. The moving coil carries current I<\/em> and produces a deflecting torque proportional to current. When the deflecting torque (proportional to I<\/em>) is equal to the control torque (proportional to \u03b8), the pointer indicates the measured value of current or voltage. Eddy current damping is given to damped out the oscillation at steady state point<\/p>\n![\"Permanent](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/permanent-magnet-moving.jpg\")
<\/p>\n
\nl = length of the core
\nn = number of turns of the coil
\nI = current through moving coil
\nK = spring constant
\n\u03b8 = deflection of moving coil
\nB = Magnetic flux density
\nA = Area of cross section of core = d \u00d7 l<\/p>\n![\"Deflecting](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/deflecting-torque.jpg\")
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\nthe half wave rectifier output (i.e., Im<\/sub> \/\u03c0 = Iavg<\/sub><\/em>).<\/li>\n
\nof the full wave rectifier output (i.e., 2Im<\/sub>\/\u03c0<\/em>).<\/li>\n
\n\u2022 The instrument is used to measure dc only.
\n\u2022 It is costly compared to moving iron instruments.
\n\u2022 It can measure current upto 50 mA and voltage upto 100 mV only.<\/p>\n![\"shunt\"](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/shunt.jpg\")
![\"Ammeter](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/ammeter-shunt.jpg\")
<\/p>\n![\"Temperature](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/temperature-compensation-ammeter-shunts.jpg\")
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\nSuch a meter is called \u201cmultirange Ammeter\u201d. A multirange ammeter is shown below in figure.<\/p>\n![\"Multi-range](\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/multi-range-ammeter.jpg\")
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\n Must Read: <\/strong> What are the Electrical and Electronics Measurements?<\/strong><\/a><\/p>\n