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An early D'Arsonval galvanometer showing magnet and rotating coil. A galvanometer is an electromechanical measuring instrument for electric current.Early galvanometers were uncalibrated, but improved versions, called ammeters, were calibrated and could measure the flow of current more precisely.
Many types of chart recorders use a galvanometer to drive the marking device. A light coil of wire suspended in the magnetic field of a permanent magnet deflects in proportion to the current through it; instead of the pointer and scale of a direct-reading meter, the recorder deflects a pen or other marking device.
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A ballistic galvanometer is a type of sensitive galvanometer; commonly a mirror galvanometer. Unlike a current-measuring galvanometer, the moving part has a large moment of inertia, thus giving it a long oscillation period. It is really an integrator measuring the quantity of charge discharged through it. It can be either of the moving coil or ...
A resistance wire is laid along the length of a metre rule and contact with the wire is made through a galvanometer by a slider. When the galvanometer reads zero, the ratio between the lengths of wire to the left and right of the slider is equal to the ratio between the values of a known and an unknown resistor in a parallel circuit. [5]
Subsequent designs of ohmmeter provided a small battery to apply a voltage to a resistance via a galvanometer to measure the current through the resistance (battery, galvanometer and resistance all connected in series). The scale of the galvanometer was marked in ohms, because the fixed voltage from the battery assured that as resistance is ...
Each notch is stamped with a number, and the wire or sheet, which just fits a given notch, is stated to be of, say, No. 10, 11, 12, etc., of the wire gauge. The circular forms of wire gauge measurement devices are the most popular, and are generally 3 + 3 ⁄ 4 inches (95 mm) in diameter, with thirty-six notches; many have the decimal ...
He next evolved the idea of the hot-wire galvanometer, or voltmeter, the value of which was universally recognised among electrical engineers. He was awarded the gold medal for this invention at the International Inventions Exhibition in London of 1885. He also originated a method of finding the efficiency of a dynamo.