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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Wheatstone bridge ： ウィキペディア英語版 Wheatstone bridge A Wheatstone bridge is an electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component. The primary benefit of a wheatstone bridge is its ability to provide extremely accurate measurements (in contrast with something like a simple voltage divider).〔"Circuits in Practice: The Wheatstone Bridge, What It Does, and Why It Matters", as discussed in this MIT ES.333 class (video )〕 Its operation is similar to the original potentiometer. It was invented by Samuel Hunter Christie in 1833 and improved and popularized by Sir Charles Wheatstone in 1843. One of the Wheatstone bridge's initial uses was for the purpose of soils analysis and comparison.〔"The Genesis of the Wheatstone Bridge" by Stig Ekelof discusses Christie's and Wheatstone's contributions, and why the bridge carries Wheatstone's name. Published in "Engineering Science and Education Journal", volume 10, no 1, February 2001, pages 37–40.〕 == Operation == In the figure, $\backslash scriptstyle\; R\_x$ is the unknown resistance to be measured; $\backslash scriptstyle\; R\_1$, $\backslash scriptstyle\; R\_2$ and $\backslash scriptstyle\; R\_3$ are resistors of known resistance and the resistance of $\backslash scriptstyle\; R\_2$ is adjustable. If the ratio of the two resistances in the known leg $\backslash scriptstyle\; (R\_2\; /\; R\_1)$ is equal to the ratio of the two in the unknown leg $\backslash scriptstyle\; (R\_x\; /\; R\_3)$, then the voltage between the two midpoints (B and D) will be zero and no current will flow through the galvanometer $\backslash scriptstyle\; V\_g$. If the bridge is unbalanced, the direction of the current indicates whether $\backslash scriptstyle\; R\_2$ is too high or too low. $\backslash scriptstyle\; R\_2$ is varied until there is no current through the galvanometer, which then reads zero. Detecting zero current with a galvanometer can be done to extremely high accuracy. Therefore, if $\backslash scriptstyle\; R\_1$, $\backslash scriptstyle\; R\_2$ and $\backslash scriptstyle\; R\_3$ are known to high precision, then $\backslash scriptstyle\; R\_x$ can be measured to high precision. Very small changes in $\backslash scriptstyle\; R\_x$ disrupt the balance and are readily detected. At the point of balance, the ratio of :$\backslash begin$ \frac &= \frac \\ \Rightarrow R_x &= \frac \cdot R_3 \end Alternatively, if $\backslash scriptstyle\; R\_1$, $\backslash scriptstyle\; R\_2$, and $\backslash scriptstyle\; R\_3$ are known, but $\backslash scriptstyle\; R\_2$ is not adjustable, the voltage difference across or current flow through the meter can be used to calculate the value of $\backslash scriptstyle\; R\_x$, using Kirchhoff's circuit laws (also known as Kirchhoff's rules). This setup is frequently used in strain gauge and resistance thermometer measurements, as it is usually faster to read a voltage level off a meter than to adjust a resistance to zero the voltage. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Wheatstone bridge」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.