Galvanometer - Galvanometer

A device that detects the presence or absence of minute potential differences or minute currents in electric circuits. It is called a galvanometer, sometimes abbreviated as galva. In addition to being used alone, many are incorporated into various bridges and used to detect the balance of circuits. They are divided into DC and AC types, and are broadly divided into moving needle and moving coil types based on their structure. However, moving needle types are rarely used today because they are difficult to handle. In the moving coil type, a moving coil with a light reflector is suspended between the poles of a strong permanent magnet. When a small current flows through the coil, a driving torque is generated and the coil rotates. As the coil rotates, the suspension wire twists, and the coil stops at a position where the generated control torque and driving torque are balanced. The presence or absence of current is detected by reading this "deflection" using reflected light. This type is usually called a reflected light galvanometer. Reflected light galvanometers can detect currents of about 10 ^-10 amperes and are used in precision experiments, but they require careful handling, such as removing vibrations and making adjustments. This was simplified by the box-type galvanometer and the pointer-type galvanometer, the former of which can detect minute currents of about 10 ^-8 amperes, and the latter of which can detect minute currents of about 10 ^-6 amperes. There is also the vibration galvanometer for AC, but it is seldom used today because it is cumbersome to use.

[Toshiharu Takao]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

電気回路の微小電位差や微小電流の有無を検出する装置。ガルバノメーターgalvanometerといわれ、ガルバと略称することもある。単独で用いるもののほか、各種のブリッジに組み込まれて回路の平衡検出に使用されるものも多い。直流用と交流用とに分けられ、構造上から可動磁針型と可動コイル型とに大別される。ただし、可動磁針型は取扱いが不便なため、現在ほとんど使われない。可動コイル型は強い永久磁石の磁極間に、軽い反射鏡付きの可動コイルをつり下げてある。コイルに微小電流が流れると、駆動トルクが生じてコイルは回転する。回転につれてつり線がねじれ、生じた制御トルクと駆動トルクとが平衡した位置で静止し、この「振れ」を反射光で読んで電流の有無を検出する。普通このタイプを反照検流計という。反照検流計では10^-10アンペア程度の電流も検出できて精密な実験に用いられるが、振動の除去や調整など、取扱いに十分な注意が必要である。これを簡便にしたのが箱型検流計と指針型検流計で、前者は10^-8アンペア程度、後者は10^-6アンペア程度の微小電流の検出ができる。また、交流用としては振動検流計があるが、取扱いがめんどうなため、現在はほとんど用いられない。

［高尾利治］

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