It's possible--of course that's the same way they make fuses. A longer, fatter wire might be better.
It's possible--of course that's the same way they make fuses. A longer, fatter wire might be better.
Recently in a non-electronics group, I heard mention of using a thin wire for resistance and a high current, low-voltage application (roughly maybe a few amps at about six volts).
What about using a thin wire in place of a resistor?
I guess some resistors are made from a thin, coiled wire, but they are insulated.
Thank-you.
-- I can measure the resistance through a thin wire, so I know the resistance.
I recently bought a spool of # 16 Manganin wire to make some home-made low-inductance precision resistors, wound on ceramic tubes. I posted a pic in a.b.s.e. a while back. Manganin has a very low tc, below 10 ppm/k typically, and is solderable. One can make a pretty good current shunt just by soldering a Manganin jumper between two plated-through holes on a pcb. We also punch or photoetch funnily-shaped current shunts out of sheet manganin.
Zeranin is even better, but is harder to get.
John
Using thin wire for resistance is common practice. They are called wirewound resistors and are manufactured by all the leading resistor manufacturers.
Ni-Chrome wire was very popular years ago. It has a high resistance, and can withstand higher currents. I'm not sure where you can get it today. I remember using "Picture hanging wire" many years ago from the five and dime, that was probably aluminum wire!
The tempco is pretty good if you use manganin wire, and not so bad with Constantan wire. Brass is not as bad as copper either.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com
No they ain't.
-- "What is now proved was once only imagin'd." - William Blake, 1793.
In article , John Doe wrote: [...]
It is a great way to make a resistor with a huge surge rating but a bad temp-co. I've used it a few times. Higher values need impractical amounts of wire.
BTW: #40 wire is just about 1 Ohm per inch.
-- -- kensmith@rahul.net forging knowledge
Actually, quite a few are, but I agree the 'wirewound resistor', does not inherently meet the definition of using a 'short length' of wire.... Look instead at 'current sense shunts'. TT electronics do a range of these, as do a couple of other manufacturers that I know of. Short lengths of wire, with ends to either go through holes, or onto surface mount tracks. Made of wires designed to give a relatively stable resistance with changes in temperature, with the big advantage, of offering very low inductance. Look at:
Best Wishes
the leading
Are you saying that wire had no resistance, or that you don't know of anyone making wirewound resistors?
Which leads me to ask: Please list the resistor manufacturers who do not in some division currently make a wirewound resistor.
Also, define "Leading resistor manufacturers" for the sake of clarity!
The only problem is that most wirewound resistors are relatively expensive, since most are considered to be precision, or power.
It depends on the application- your description makes it sound like you are after a high current low resistance resistor. There are precision milliohm high current resistors with 30ppm/oC stability and specially designed to uniformly diffuse the heat out of the package. A copper wire has 3900ppm/oC stability and undefined heat removal characteristics, comparatively a piece of junk.
I don't know how her prices compare to eBay, but Lawrence Lile (an EE of my acquaintance) has a daughter wot sells nichrome wire for spending money right here:
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com
One of Bob Pease's colums was about doing this (well, thicker wires for a very low resistance). He made a round squirrelcage thing (distributes the current to each wire equally) of wire with the wires far enough apart so each wire doesn't heat up much, so the value doesn't change much. Here's the article:
-----
Manganin has a parabolic curve of resistance vs temperature, peaking at some temperature and falling off above or below. Within maybe 10 deg C of the peak, tc is only a few PPM. The peak temp depends on the manganese composition and on the alloy's history - mechanical stresses, like winding or fabrication, mess up the curve, and annealing fixes it. You can buy "wire" manganin with zero tc (parabola peak) near 25C, or "shunt" manganin with min tc around 80 c or something, for big shunts that self-heat a lot. One alloy is "manganin
13" (13% manganese) and one is "manganin 12" but I can't remember which is which.I can post some data and curves to a.b.s.e. if anybody's interested. I have that stuff at work.
John
For limited temperature range, and low self-heating, I've found that
1/4" copper pipe worked just ducky for a 300Amp shunt.(For a golf cart motor controller :-)
...Jim Thompson
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et |
We punch and photoetch shunts from manganin sheet stock. I have some curves of r-vs-t for as-punched and after annealing. This is *very* tedious data to acquire! We anneal the stuff at 150C for 24 hours or so, which seems to calm it down. It oxidizes them too, so we dunk them in dilute HCl before we try to solder them. Manganin is solderable with agressive flux, but not super-easily.
Harrison Alloys used to be the prime manganin supplier, and they had lots of nice tc and annealing data. The company seems to keep changing hands, became Harris-Driver I think, but I can't locate them on the web. Last time I talked to them, some years ago, they didn't know much about the stuff; it was sort of like a recipe they'd inherited. They apparantly also made good batches and bad batches, sort of at random.
Manganin doesn't laser cut very well... too reflective or something. Gums up milling cutters, too, like machining acrylic. Punching is good, but the dies are expensive. Lately we photo-etch, cheap and low-stress.
John
Careful- there's more than one alloy called Constantan and more than one called Manganin-- I think I'd only trust data direct from the alloy manufacturer. There are only a handful of companies world-wide that make these alloys. Carpenter, Hoskins, Johnson-Matthey (precious metal alloys), etc.
Carpenter shows Manganin 13 (9.5% Manganese, 86% Cu, 4.5% Ni) tempco as +15ppm/K (average over some unspecifice range!), but the actual tempco varies considerably over the normal operating range, peaking at about 45°C, and actually goes negative below about 25°C and above about 75°C.
Managanin 130 (12% Manganese, 84% Cu, 4% Ni) has a more negative tempco that peaks at about 30°C.
To John Larkin: Interesting they recommend aging the material at
120-138°C for 25-48 hours to improve the stability. That's for wirewound resistors, but I imagine it would apply to other forms that have been formed, laser cut, or machined.Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com
According to Tennent the Invaluable (1989 edition)
Constantan + or - 4 x 10e-5 Manganin + or - 1 x 10e-5
Paul Burke
I've been trying to find some decent data on the tempcos of Manganin, Constantan and Nikrothal LX (or any other low TCR material) for a while now - preferably a typical resistance vs temperature curve, but the best I've been able to Google is that Manganin is either 10 or
15ppm/K, Constantan is either 20 or 74ppm/K (but over a wider range), and Nikrothal LX may be 10 ppm/K - not quite enough consistency to give me any confidence at all. Any chance you can point me to some credible data (ideally over the range -40C to +60C)? Even better, a trusted supplier? in Australia?Tony (remove the "_" to reply by email)
You can always measure the temperature with an NTC and calculate it out...
Rene
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