"Shunt" Resistors

I recall designing circuits for analog meters with current shunt resistors. In the last thirty years my measurements are all done by measuring voltag e across series resistor. Is this resistor still referred to as a "shunt"? Even though it is no longer shunting current around a current meter, obso lete terminology often remains. An example is calling the AC-DC power supp ly in an LED replacement for a fluorescent lamp a "ballast".

Do you refer to the series current sense resistor a "shunt"?

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  Rick C. 

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Ricketty C
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A series resistor is not a "shunt". It is a current sensing resistor. A shunt resistor is in parallel with the meter. If you parallel one resistor with another, it can be considered a shunt resistor. If you put a resistor in series with another resistor to read the current, it is not considered a shunt resistor.

Feel free to call them whatever you like.

Reply to
John S

Right. It doesn't care what you call it.

We used to make our own current shunts from sheet manganin. We had them punched, and we annealed them to relieve stresses. They drove diffamps in NMR gradient amps, not meters. We epoxied them to temperature-controlled metal blocks, which had interesting eddy-current effects.

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Digikey will sell you surface-mount "current shunts", which just means a very low value resistor intended for current measurement. They are typically solid metal, not cermet, and sometimes have 4 leads.

Jumpers are sometimes called shunts too.

Reply to
John Larkin

We made our own shunts too, for a while out of Cupron wire. Tough stuff to bend into a loop that is repeatable and stuffable. So we had a spring company do that. Works great.

The industry calls them shunts AFAIK too even through they are series resistance. Canadian Shunts is one company we used for 500 amp at 50 mV

Yes, we use the jumper shunts as well. Those may be seires or parallel in circuit operation...

So, when you have a battery and a light bulb connected together, just two components, is that a parallel or a series circuit ??

boB

Reply to
boB

BITD a 'meter shunt' was a resistor whose tempco matched that of the copper winding of your analogue meter movement, and whose resistance was some convenient submultiple of the meter's resistance, like 1/99 to turn a 1-mA meter into a 100-mA meter.

Nice not to have to worry about that anymore.

Cheers

Phil Hobbs

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Reply to
Phil Hobbs

Yeah but it's in series with the load, a current-sensing resistor. just sayin'.

Reply to
Bob Engelhardt

Both terms are simple and quick expanations of a component's function.

This practice is sometimes mis-used, but I think you've picked the wrong examples to shake your stick at.

RL

Reply to
legg

Of course, but if you ordered a current sensing resistor with a tempco of +3000 ppm/K you'd be disappointed, whereas that's about right for a meter shunt. So the distinction is entirely worthwhile.

Cheers

Phil Hobbs

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Reply to
Phil Hobbs

The manganin sheet stock that we bought had a zero TC around 60C, which was the temperature of the heated block that we glued our shunts to. One can also buy manganin that has its flat spot at room temp.

Punching and bending wrecked the TC, and annealing fixed it again.

Other alloys, like zerodur and something else, were much better but hard to get.

We needed wideband current sensing to make PPM-precise pulses, and got interesting eddy-current effects (looked like series inductance, make voltage overshoots) from the shunt being flat against the aluminum block. We found a fix for that.

Annealing is a black art. I knew a French guy who got the permeability of metglas up to 1e6 by a secret annealing process.

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John Larkin         Highland Technology, Inc 

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Reply to
jlarkin

We use a lot of shorthand terms that make language purists who don't design things get all prissy.

Too bad.

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John Larkin         Highland Technology, Inc 

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jlarkin

snipped-for-privacy@highlandsniptechnology.com wrote: [Snip ...]

Julien Bergoz, I'm pretty much certain. Sadly, he passed away.

Jeroen Belleman

Reply to
Jeroen Belleman

Sad. He was a cool guy, sort of a French teddy bear/hurricane.

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John Larkin         Highland Technology, Inc 

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Reply to
jlarkin

He was a colourful character. The first time I met him, he was playing golf on the tiny front lawn of a hotel in Frascati, Italy, sometime in the 1990s. He was the originator of the 'Faraday Cup', a reward for outstanding contributions to the field of particle beam accelerator instrumentation. He was enthusiastic about "Goubeau lines", some arrangement he saw as useful for testing current transformers. I never quite got the hang of what was so great about those.

His company, Bergoz Instrumentation, continues.

Jeroen Belleman

Reply to
Jeroen Belleman

An electricity meter manufacturer I am familiar with use a manganin strip electron beam welded to copper busbars to avoid some of these issues - especially the avoidance of contamination and stress.

Narrow slots milled into the surface of the Al block or insulating spacer?

Yes, I used to anneal Mumetal in a hydrogen atmosphere. It made the workshop manager very nervous.

John

Reply to
jrwalliker

That's a little bit funny. A hydrogen atmosphere is not really any more dangerous than oxygen. We breath that stuff! It's when the two are mixed that you can have problems. I assume this would have been in a small volume?

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Reply to
Ricketty C

hydrogen only takes a few uJ to ignite, it burns in any ratio with air from 4-75%, explodes in mixtures from 18-60%

Reply to
Lasse Langwadt Christensen

I think the chamber volume was around 0.5l and the excess hydrogen was burned off with a small flame outside the furnace. I thought it was safe. I also used oxy-hydrogen in a miniature welding torch for welding platinum. The torch had sapphire jets.

John

Reply to
jrwalliker

Even though that would technically be a current sense resistor some still call it shunt. Or in the UK "shoont" :-)

Same as some people call an electronic dimmer a rheostat. It's wrong but everyone old enough knows what is meant.

The first one I learned in industry was "fudge factor". Our professors would have been disgusted.

[...]
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Joerg

you can get a cheap Chinese electric,

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Reply to
Lasse Langwadt Christensen

It doesn't burn at 100% hydrogen. That is my point.

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  Rick C. 

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Ricketty C

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