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'[EE:] Anyone know anything about galvanometers?'
2012\05\22@090547 by rchadwic

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subject=Re:[EE:] Anyone know anything about galvanometers?
Up until the change to digital and DSP technology, galvanometers were used as the amplifying elements in seismometers. They were (are) much less sensitive to variations in leakage and offset currents than operational amplifiers, and can be made to have large gains when combined with optics, mirrors and a good, solid platform (vibration-free).
        I never had the opportunity to work with them while I was in the Air Force, but talked a lot with techs that did.  You might find some application info googling under seismology or thereabouts.
Bob Chadwick
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2012\05\22@211324 by graham foulkes

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The galvanometer shown in the photos looks like a classic D'arsonville
mirror galvanometer, sometimes called a spot galvanometer as a light beam
takes the place of a needle pointer.. It looks like it could be a torsion
suspension type with the coil and  mirror suspended on a quartz thread if
there are no signs of pivots or point bearings. Not easy to tell from the
photos but I suspect there are parts missing. The cover is to prevent the
delicate suspension from being affected by air currents. A light source
placed external to the galvanometer is essential to the operation of the
instrument as is an external scale placed at a distance from the mirror.
The sensitivity is multiplied by the arc / distance. These were capable of
recording micro amp currents flowing in circuits. The sensing coils were
usually of several thousand ohms resistance, very fine wire!

On Tue, May 22, 2012 at 9:05 AM, rchadwic <> wrote:

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