Electronics > Projects, Designs, and Technical Stuff
Building a current shunt?
TERRA Operative:
Thanks for the info all!
I've been looking around at resistance wires, and I think I have an idea...
Looks like Kanthal wire has decent specs, 1.45uohm/mm resistivity (roughly equivalent to nichrome wire), but half the temperature coefficient at 49ppm/oC from what I can find.
I roughly calculated that 8 strips of flat wire 4mm x 0.3mm at 630mm long each will give me about 0.1ohm, which I can then trim to spec.
Kanthal looks relatively cheap, so I was thinking of getting some to have a play with. I'll maybe try clamping the 8 parallel wires between some brass blocks at each end and then running them back and forth to compact it a bit, kind of like the one in the photo posted by ArthurDent.
Anyone know the temperature coefficient of brass by chance?
beanflying:
Generally if you use a decent sized lump or Brass or better Copper you can ignore it's T/C relative to the wire or strip.
Last time I got some Kanthal wire I used this evilbay seller. Postage was about two weeks depending on what your local availability is https://www.ebay.com.au/usr/resistance_wire?_trksid=p2047675.l2559
TERRA Operative:
Cool, I plan to use a reasonably sized lump of brass.
Also, I found that seller, I already had my Kanthal wire selected from them. :)
pwlps:
For high currents and high accuracy a DCCT might actually be cheaper than a big high quality shunt. I found some on ebay for less than $100.
Kleinstein:
Kanthal is a difficult to solder material. It is suitable material for high temperature heaters, not so much resistors. The more obvious choice is Manganin, as it is lower resistance, low thermal EMF, low TC (often < 10 ppm/K) and it is relatively easy to solder. There is a reason that most of the low ohms shunt are made from this alloy. A possibly source for the material could be lower resistance shunts. These tend to be made from several layers, that could be separated and possibly put in series.
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