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Electroscopes, Electrometers, High Voltage Meters.

The electrometer at right was made starting in 1845 by Watkins & Hill, instrument makers in London. The instrument is supposed to measure the forces between small bodies charge with electricity. A thin bar of insulating material, suspended from the top with a silk filament holds horizontally an electrical conductive ball balanced by a counterpoise. Electrified bodies were introduced through the lateral hole and the degree of deflection was supposed to measure the force between the two bodies.

The Watkins & Hill torsion balance was promoted for many years to yields accurate estimates of the forces between charged bodies. However, the proper functioning of such instrument is highly questionable. The small diameter of the instrument (five inches), the unshielded glass construction, the lack of moisture prevention features makes the apparatus more a symbol of the inverse square law of electrostatic force than a functional device.


Electrometer by Central Scientific


The apparatus at right is of “Braun Electroscope” type. It was created by Professor Ferdinand Braun of Tubingen Germany, early in the early 1900. It is primarily used for classroom demonstrations of electrostatic phenomena. The Braun's original version is housed in a box.


Below is a standard Dolezalek quadrant electrometer of unknown manufacture. Possibly German.
As is almost always the case, the quartz suspension fiber is missing. The body is mostly stainless steel while the outer protective case is painted brass. Four amber insulating posts support the polished brass quadrants. The vane, not visible, is coated paper.
The electrical connections for the quadrants, not visible in the photo, are on the bottom of the instrument.








Tne Lord Kelvin multicellular voltmeter in the right is made by Kelvin Bottomey & Baird probably in the 1930s. The instrument has a removable dashpot under it to house an oscilation dumping vane. Instructions indicates that the Casor oil, provided in the carring box, should be removed during transporation. No need to wory about this any more, it will not splash, it hardened up! The green color probably should be attributed to corrosion inside.

The instrument is a "modern" version of the multicellular voltmeter developed by Thomson in 1887. The aparatus at right is in Harvard Colection.

An instrument very similar with ours, with tag number 2900, Mfg: Kelvin & James White, Ltd. is in Caltech collection.

central scientifique electrometers
The tho electrometers pictured above, are very similar in shape to the Watkins & Hill instrument. Made by Central Scientific. A major improvement: would be the methalic body of the apaaratus. (shilding by Faraday effect). But are those instruments electrometers? The only thing inside is a heavy iron ring , most likely there to dumpen oscilation.










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