Galvanometers

[PGBerrie]

Galvani was the guy with the twitchy frog's leg - the moving-coil galvanometer was invented by d'Arsonval. The "galvano" bit is just to honour the discoverer. Like Ohm, Volt, Watt, Colomb etc. Pity there's no Gresley!

Peter

[52D]

Do ten Thompsons make a Peppercorn and Ten Peppercorns equal one Gresley?

[Atlantic 3279]

Silly me, I wasn't thinking! Power x time would presumably calculate the energy, in Joules...

Yes, of course charge = current x time. But I still suspect that if used in such a way as to be described as a ballistic galvanometer, a charge measurement is possible. Funny how the recollection of A level physics practical textbooks never totally vanishes.

[Bryan]

[quote Funny how the recollection of A level physics practical textbooks never totally vanishes.[/quote]

Until you need it

[geofrancis]

Harvesters comments remind me of using a 2ohm variable shunt to test track circuits to check at what point the track circuit relay operates (about .6 ohms comes to mind) , still not sure where the galvo came in, but was to do with the same testing.
Its 70 years ago.
geofrancis

[geofrancis]

Harvesters description reminds me of tests we carried out on track circuits and the use of shunts.
We used a variable 2ohm shunt to check ar what point the relay would operate when a train was on track, the value of .6ohms comes to mind, the use of the Galvo was used in a simular way, but for what reason escapes me. mind you this was 70years ago
Geofrancis

[Colombo]

Flamingo mentions the hot wire galvanometer.

Could this be the device that I once used to use to measure the temperature in a furnace. The colour of a very hot object is dependant on its temperature of course. You looked into a furnace through a device like a camera viewfinder across which was stretched a wire filament through which a current was passed which heated the wire. You adjusted the current until the colour of the wire matched that of the object of interest in the furnace and then read the temperature off the dial.

It might have applications in a loco firebox, investigating slag on the firebars for example, which might be due to poor quality coal with a low ash fusion temperature.

Colombo

[Belvoir]

I think your instrument would have been a Hot-wire Pyrometer ........

If my failing memory is to be believed, a hot-wire galvanometer indicated the current flowing through the hot wire by mechanically amplifying the thermal expansion of said wire - but it was a loooooong time ago.

Cheers

[geofrancis]

The 2ohm shunt I referred to was a small box with about 8/10 equal increments which you started from the zero point and wound up until the track circuit relay dropped out, as I said I think 0.6ohm was the recommened value. The shunt of course was connected between each rail.
geofrancis