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18

The electrometer can be used as an oscillograph by using a high potential difference between the plates, say, from 40 to 200 volts, with the fibre tightly stretched.

The microscope has a tube 10 inches long, supplied with a Zeiss achromatic objective C, and a No. 3 micrometer eye-piece. For visual work with this arrangement, one division of the eye-piece micrometer corresponds to a movement of the fibre of 0’0038 mm. approximately. The instrument can also be adapted for photographic work, or for projection on a screen.

Dolezalek Quadrant Electrometer.

11A Damped Quadrant Electrometer for Submarine Cable Testing,” “ Electrician,” November 12th, 1909.

This instrument is of the “ Quadrant ” type, and is mounted upon ambroid pillars, affording very high insulation. The needle is of paper,, thinly coated with “ silver paper,” of a form ensuring ample rigidity. It is suspended by a quartz fibre, which renders the instrument very sensitive. The needle and quadrants being small, the electrostatic capacity is also small. The motion is very nearly dead beat, the deflections being proportional to the potential differences producing them.

A small plane mirror is attached to the needle, which is suspended from the quartz fibre by a V hook in such a way as to prevent slip. Two adjacent quadrants are hinged so that they can be swung open to allow of easy access to the needle. The needle is charged by a simple charging rod.

The base is supported by levelling screws, and the whole of the instrument can be rotated in a horizontal plane about this base, and clamped in any position. The suspension is provided with a torsion head, and a brass cover serves to prevent electrostatic forces from affecting the working of the instrument. This cover is fitted with a lens of 100 cms. focus.

The extreme lightness of the moving system renders it very sensitive. Three quartz fibre suspensions and one of phosphor bronze are supplied, so that a very wide range of sensitiveness can be obtained.



Le texte affiché peut comporter un certain nombre d'erreurs. En effet, le mode texte de ce document a été généré de façon automatique par un programme de reconnaissance optique de caractères (OCR). Le taux de reconnaissance estimé pour cette page est de 99,65 %.

La langue de reconnaissance de l'OCR est l'Anglais.