MIRROR GALANOMETER BY H.TINSLEY, 1960's

Mirror Galvanometer made by H. Tinsley. A mirror is fixed to an armature and hung on a gold thread between an electromagnet, the mirror moves according to current in the coil. A light is reflected off the mirror onto a distant scale amplifying the reading. Used for measuring small electrical currents this was the most sensitive means of measuring currents during the early years of electronics. Galvanometers were used by the Post Office Telegraphy departments for detecting signals over very long lines.

See Item A0913 below where one is being used with a viewing screen.

A1613

ADAM HILGER MIRROR GALVANOMETER WITH VIEWING SCREEN, 1950's

A mirror galvanometer is a mechanical meter that senses electric current, except that instead of moving a needle, it moves a mirror. The mirror reflects a beam of light, which projects onto a meter, and acts as a long, weightless, massless pointer. In 1826, Johann Christian Poggendorff developed the mirror galvanometer for detecting electric currents. The apparatus is also known as a spot galvanometer after the spot of light produced in some models.

Donated by Ken Willis

A0913

MIRROR GALVANOMETER AND STAND, 1950's

Calibrated scale for use with Mirror Galvanometers such as Items A0880. A0191 and A0202. The dot of light reflected by the mirror in instrument is displayed on scales like these.

Donated by Desmond Squires

A1376

PHILIP HARRIS MIRROR GALVANOMETER, 1950's

The mirror galvanometer was later improved by William Thomson, later to become Lord Kelvin. He would patent the device in 1858.
Thomson reacted to the need for an instrument that could indicate with sensibility all the variations of the current in a long cable. This instrument was far more sensitive than any which preceded it, enabling the detection of the slightest defect in the core of a cable during its manufacture and submersion. Moreover, it proved the best apparatus for receiving messages through a long cable.
A mirror galvanometer is a mechanical meter that senses electric current, except that instead of moving a needle, it moves a mirror. The mirror reflects a beam of light, which projects onto a meter, and acts as a long, weightless, massless pointer. In 1826, Johann Christian Poggendorff developed the mirror galvanometer for detecting electric currents. The apparatus is also known as a spot galvanometer after the spot of light produced in some models.

A0202

CAMPBELL VIBRATION TYPE No 106 MIRROR GALVANOMETER of 1912

Mirror galvanometers were used extensively in scientific instruments before reliable, stable electronic amplifiers were available. The most common uses were as recording equipment for seismometers and submarine cables used for telegraphy.
This model made by the Cambridge and Paul instrument Co has a mirror suspended from two threads instead of one. And is known as a Bi-filar type. Originally conceived by Albert Campbell. See the history above.
In December 1919 the Cambridge Scientific Instrument Company took over the smaller but successful Robert W. Paul(1869-1943) Instrument Company and became The Cambridge and Paul Instrument Company Ltd.

• View with cover removed
  

A0191

CAMBRIDGE INSTRUMENTS MIRROR GALVANOMETER, 1950's

Mirror Galvanometer standard design of the period. These instrument were becoming obsolete as Oscilloscopes were taking over,and have in this form have fallen out of use. Mirror galvanometer systems are now used as beam positioning elements in laser optical systems.

A0880

CAMBRIDGE SPOT GALVANOMETER, 1950's

Spot Galvanometer with a 450 ohm movement made by Cambridge Instruments. In working order.

Donated by L.G.Bray

A1521

WESTERN ELECTRIC GALVANOMETER

Made by the Western Electric Company in America during 1918. A moving coil meter called in this case a Galvanometer, with a full scale deflection of 20 Milliamp s, today it would be called just a moving coil meter. The movement is made by WECO (Western Electric Company) and the horseshoe magnet made by Weston Electric Company.

Nortel Collection

A1355

CAMBRIDGE UNIPIVOT GALVANOMETER, 1920's

Based on Jacques Arsene D'Arsonval's moving coil galvanometer, manufactured on a large scale by the Weston Electrical Instrument Company of Newark, New Jersey, Robert William Paul (1869-l943) devised an instrument in which the moving parts were supported on a single bearing giving lower friction and therefore greater sensitivity. Other unipivot instruments followed. His instruments gained international recognition, winning gold medals at the 1904 St Louis Exposition and the 1910 Brussels Exhibition. In November 1919, his business was bought by the Cambridge Scientific Instrument Company, which was renamed "The Cambridge and Paul Instrument Company." Cambridge Scientific Instrument Company was a company founded in 1881 by Horace Darwin (1851-1928) and Albert George Dew-Smith (1848-1903) to manufacture scientific instruments. Their partnership became a Limited Liability Company in 1895. In 1920 it took over the R.W. Paul Instrument Company of London, and became The Cambridge and Paul Instrument Company Ltd. The name was shortened to the Cambridge Instrument Company Ltd. in 1924 when it was converted to a Public limited company. The company was finally taken over by the George Kent Group in 1968, forming the largest independent British manufacturer of industrial instruments.

A1333

GRIMSDELL DIX GALVANOMETER, 1900's

Astatic galvanometer made by Grimsdell Dix Acton London. An Astatic type has two needles in parallel mounted in opposite direction, to defeat the effect of the earth's field.

A0192

W G PYE CO LTD TANGENT GALVANOMETER, 1900's

A tangent galvanometer is an early measuring instrument used for the measurement of electric current. It works by using a compass needle to compare a magnetic field generated by the unknown current to the magnetic field of the Earth. It gets its name from its operating principle, the tangent law of magnetism, which states that the tangent of the angle a compass needle makes is proportional to the ratio of the strengths of the two perpendicular magnetic fields. It was first described by Claude Servais Mathias Pouillet in 1837.

A0754

PHILIP HARRIS TANGENT GALVANOMETER, 1900's

Used for measuring very small currents of electricity which when passed through the coil would deviate the needle from the magnetic north. See A0754.

A0258

PHILIP HARRIS GALVANOMETER WITH SCALE, 1950's

A mirror is hung on a gold thread between an electromagnet , the mirror moves according to current in the coil. A light is reflected of the mirror onto a distant scale amplifying the reading. Used for measuring small electrical currents by amplifying the movement of an armature with a mirror attached to it suspended between a coil. A light is shone onto the the mirror and reflected onto a scale some distance away. This model has a needle and scale also

A1547