Should a shunt for a copper-coil moving coil meter be copper also?

For higher current readings, such as 100 amps, a 100 mV shunt dissipates

10 watts, which can cause significant heating above ambient. So unless the meter movement is in close thermal proximity, the temperature of the shunt will be much higher. This is why shunts are made from low tempco materials.

The 1000 ohms for the 50 uA movement is about what I would have expected and close to my recollection that a 100 uA meter would be about 500 ohms. In

fact, it may even be less, since it requires half the number of turns for twice the current, and those turns could be a thicker wire.

That being said, I have a 100-0-100 uA Model 1120 blank scale edgewise meter, essentially 200 uA FS, and the movement measures 536 ohms at 62F.

Paul

Hmmm, I hadn't heard of either of them. Cupron seems to be a trade name for constantan. (AFAICT)

George H.

For the meter, yes. The shunt will dissipate about a watt at 10A.

Consider the temp rise of 1 Watt dissipated by 44 cm of wire vs 0.67 cm. Its not a trivial problem, but the copper wire is about 65 times as long. More surface area, greater dissipation, less temp rise and less need for a low tempco shunt wire.

--
Paul Hovnanian     mailto:Paul@Hovnanian.com 
------------------------------------------------------------------ 
Don't hate yourself in the morning -- sleep till noon.

"Paul Hovnanian P.E."

** That simple fact was posted here by me 9 dys ago.

Do try reading the WHOLE thread !!!

** Not a problem - Nichrome has a near zero tempco. ** Bullshit.

**That is a big problem.

Fuck off fool.

..... Phil

No. Its about 4*10^-4/°C.

And 1 Watt dissipated by a 0.67 cm x 1mm wire is beginning to look like a light bulb filament.

Well then, educate us. What will the temp rise of that wire be?

The resistance of the shunt will vary with the temp rise times this temperature coefficient.

--
Paul Hovnanian     mailto:Paul@Hovnanian.com 
------------------------------------------------------------------ 
Free the Mallocs!

"Paul Hovnanian P.E. is glutton for punishment "

** Wrong !!!

Standard Nichrome is only 1.7 exp-4 per degree C in the range from 20C to

100C.

It gets much less at high temps too.

** Utter crapology.

Such a NiCr wire can be attached to a pair of hefty copper terminals that screw onto the back of the meter - heatsinking it very nicely. Another way is to use a short, flat strip necked down in the centre and trimmed to the exact value and bolt that on the back.

** Fuck all.

Piss off - you TROLLING DAMN FOOL

... Phil

"Paul Hovnanian P.E. is glutton for punishment "

** No. YOU are a nitpicking bullshit artist.

** FFS - you arrogant lying pig.

YOU used a * WRONG * value !!!

** So that is what this insane tie raid is all about ??

You grossly over interpreted my post and moved the words completely out of context.

I merely compared 1mm copper and Nichrome wire.

I did NOT attempt to supply detailed instructions on making a shunt.

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FYI:

Go straight into HELL you INSANE nit picking FUCKWIT.

..... Phil