TheRadioBoard

I picked up a very old wooden case at a car boot sale (flea market). The base had two brass contacts at the front, a small window in the centre and inside was the following curious item - mounted firmly in place with heavy bolts.




The coil in the centre seems to have been previously mounted to the two contacts at the far ends and is suspended around a circular rod.



The contact at the bottom has an additional contact wire.



If anyone can help me identify this thing I'd be very grateful. Inside the box was also a tiny circular mirror (say 3-4mm circular) which looks like it might have been glued to the wire at some point (in the window?).



Help? I'd like to know if it's worth re-assembling or even safe to fire it up! Otherwise, the case is destined to be a radio build along with all the nice brassware (even a little window to see the coil!).

At the moment I have all the brass parts in a strip-n-dip solution to polish them up as there was some very nice heavy brass knurled hut heads.

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Galvanometer movement.

Wow. Hi Mike. Thanks for the simple answer. Not being a scientist I had no idea. But now...

From Wikipedia:
Mirror galvanometer
Extremely sensitive measuring equipment once used mirror galvanometers that substituted a mirror for the pointer. A beam of light reflected from the mirror acted as a long, massless pointer. Such instruments were used as receivers for early trans-Atlantic telegraph systems, for instance. The moving beam of light could also be used to make a record on a moving photographic film, producing a graph of current versus time, in a device called an oscillograph. The string galvanometer was a type of mirror galvanometer so sensitive that it was used to make the first electrocardiogram of the electrical activity of the human heart.

I wonder if it is worth restoring it now.

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Having seen your other handiwork, I'd say, 'definitely.' -Mike-

Looks "terminal" to me.

Another point about the mirror is that the reflection from the mirror moves through twice the angle that the coil rotates through. This gives a 2:1 "magnification" of the reading.

.....................................

GOLFGURU- Terminal indeed. Currently on sale on Ebay for spare parts The cabinet is destined to be made into a radio.

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The added parts are a single-pole switch and a rheostat bypassed by a capacitor. But that circuit appears to be shorted when the lid is closed. Someone turned a valuable object into a piece of junk.

Edit: rats. got this in wrong thread...

73,

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Sold on Ebay for more than I paid so it must be worth something (to the lucky bidder). Photos of the restoration/rebirth to come.

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