A electrometer (also called electroscope ) is a scientific measuring device allowing measurement or the description of the electric Charge of a body.

History

Research on the communication of electricity, in History of the royal Academy of sciences. 1746, 460 : “No matter what one did not discover yet of Electrometer, i.e., of instrument suitable to measure the différens degrees of electricity which a body can have…”

The apparatus itself is developed by Volta towards 1780.

“The atmospheric electricity was rather considerable, since the electrometer of Mr. Saussure, held with the hand, to the height of approximately five feet, indicated three degrees, while with ground it marked only one of them and half. ”
Travel of Perugia, T. 4, 1797, p. 4.

Principle and types of electrometers

A standard electrometer is composed of two fine sheets of Or suspended with a electrode. When the electrode is charged, the sheets are pushed back mutually. The measurement of their separation is the direct measurement of the load of the electrode.

Another way of building an electrometer is to suspend two sheets of Aluminum or Cuivre, on a cable of tantalum, Platine, or on a simple filament of Nylon.

The electrometers are discharged by a issuant Radiation Ion. Most common of the measuring instruments of radiation, the Dosimeter, is in fact an electrometer gauged, and made more robust.

The term is also used for one to name a particular type of thermionic valve. This type of valve does not have a negative deviation on its grid of control. A weak current circulates on the grid, and is amplified by the Anode. These valves can detect currents as weak as some Femto - amp S. They are very sensitive and can be destroyed by a handling without glove: the salts left by the sweat of the hands on the part out of glass of the apparatus can provide an alternate way for these weak currents.

The electrometers are used in Nuclear physics, because they are able to amplify the weak photovoltaic currents , created by radiations. But they are however supplanted more and more by the measuring devices with Semi-conducteur S.

External bond

• image of old electrometer (when electronics did not exist).
• Principle of operation
• Of building an elementary electroscope

See too

• electron
• Radiation

Homonymy

One indicates sometimes by electrometer, a completely different apparatus (see electropsychometer, which is a " invention" of the guru of the sect Scientology : Ron Hubbard )

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