MANGANIN / ZERANIN enamelled wire availability

[zhtoor]

Precision wire wound resistors require considerable knowledge and experience to produce high accuracy, high stability and low TCRs and the more exact precision you want, the harder it is to make, there are a great many variables present in manufacturing such resistors and is best left to those who are experienced at it.

Don't know the age of Edwin G. Pettis, but at a certain point it would be great he transfers all his knowledge of making precision wirewound resistors to someone, before he retires or ... . Otherwise we end up with the same situation when Jim Williams or Bob Pease passed away, a loss of knowledge.
I guess I'm not alone with this opinion, that's why most of the guys here on this forum try to find out as much as possible from Edwin on one or the other way.

-branadic-

hello -branadic-,

if you don't mind, let me say that it is the newer generation (that is us) who are mostly at fault. we do not value our elders the way we ought to.
we do not revere them, we do not cherish them, we do not appreciate them, and that is mostly the reason we are creating our own loss,
because, because of our callous attitude towards our elders, they are not sympathetic to us (and rightly so!).

it is we, who have to mend our ways.

really best wishes, i do not intend to malign anybody, and especially not you.

regards.

[CopperCone]

There is only so much that you can do to a metal.

you can

1) alloy it with something
2) offer some kind of heat treatment/cryo treatment (change its crystalline form)
3) put it under some amount of stress

 
ALSO, brazing is not hard. You just need to get some high silver (55%+), or gold alloy ($$$$) braze (both stick to anything) and a torch. A home depot mapp/oxy would probobly do, or something like a smith jewlers torch.. between $50-$400$ (not absurd considering the cost of the instruments and materials).

loose wire will be more sensitive to shock and vibration (allows it to deform) but it will be more resistant to thermal changes (strain gauge error)

tightly wound/potted wire will be less sensitive to shock and vibration but you have parasitic strain gauge effects.

I think you can figure it out. Also, with metals you can purify them by heating them in a reducing environment (i.e. hydrogen) (like how you treat mu metal after its bent)

perhaps you need to anneal coils in a hydrogen furnace after you bend (deform) them to increase stability


it seems a knowledge of metallurgy is required.

[Conrad Hoffman]

Ha! Watch out on the Smith Little Torch. The real thing is supposedly a great product, but the world is full of bogus knock-off copies. They sell for about $40-80 and are dangerous junk. They leak, the threads don't fit and there's no sapphire in the tips. The tip off is the gas knob is blue. It's supposed to be green and Smith has never ever used a blue knob, only green. I just bought one, discovered it was a fake, and returned it. My plan was to use it for silver brazing resistance wire!

[Cerebus]

perhaps you need to anneal coils in a hydrogen furnace after you bend (deform) them to increase stability


it seems a knowledge of metallurgy is required.

Yes, it seems that it is. https://en.wikipedia.org/wiki/Hydrogen_embrittlement

Now I may not be a metallurgist, but it seems to me that suggesting taking steps that are going to chemically alter alloys carefully formulated to have particular characteristics is not the wisest course of action to suggest.

Further, if a $6 PWW resistor is out of reach in the OP's country, then recommending a $400 torch is perhaps not the thing to be doing.

[zhtoor]

i understand from Edwin's comments that ceramic is probably the best substrate to do experimental manganin wire resistors,
but while i acquire ceramic substrates (bobbins or plates), how about using a glass microscope slide wrapped in kapton tape,
like the one in:-

https://www.amazon.com/3M-5413-Polyimide-Silicone-Adhesive/dp/B009OWZUYQ/ref=sr_1_3?ie=UTF8&qid=1497375354&sr=8-3&keywords=3m+5413

and using the resultant as a "card" for winding resistors on?

any comments shall be highly appreciated.

regards.

[Vtile]

If you use glass (microscope slides) you can also form it with regular propane torch, that is if it is so called soda-lime glass and not borosilicate aka pyrex^tm etc.
This way you might get the sharp edges out or use some regular window glass for the first experiments.

The trap is that it might explode while working with it or while cooling it after.  The trick is to cool it slowly to not allow the internal tensions to form if it tends to shatter while cooling.

[Conrad Hoffman]

Mica gives you a thinner resistor and thus less inductance. Glass should work- you can use a diamond hone to round the edges (do it wet). So many mica card resistors have been made by so many people, I don't think they're rocket science.

[Vtile]

x-snip-x So many mica card resistors have been made by so many people, I don't think they're rocket science.

Nope, found in every toaster in kitchen

[zhtoor]

and what would be the way to "anneal" the wound manganin resistor on either glass slide with honed edges or mica?
what kind of temperature treatment would be required to sort-of pre-age these resistors? assuming manganin or zeranin wire is used.

regards and thanks again for your valuable comments.

[CopperCone]

perhaps you need to anneal coils in a hydrogen furnace after you bend (deform) them to increase stability


it seems a knowledge of metallurgy is required.

Yes, it seems that it is. https://en.wikipedia.org/wiki/Hydrogen_embrittlement

Now I may not be a metallurgist, but it seems to me that suggesting taking steps that are going to chemically alter alloys carefully formulated to have particular characteristics is not the wisest course of action to suggest.

Further, if a $6 PWW resistor is out of reach in the OP's country, then recommending a $400 torch is perhaps not the thing to be doing.

http://mumetal.co.uk/?tag=hydrogen-heat-treatment

perhaps he has a friend with a torch or knows a welder. They like to use gas in poor countries because its cheap. It's everywhere. You can probably go to a scrap yard, buy a guy a sandwich and he will do it for you. It's not impossible to do with a big torch, a small one is just harder to overheat with. Also any jewelry designer will have one. Or car mechanic.

I am just giving my ideas. Also, you can polish wire. I'm not sure what else you can do with it to change its characteristics.

[Cerebus]

http://mumetal.co.uk/?tag=hydrogen-heat-treatment

perhaps he has a friend with a torch or knows a welder. They like to use gas in poor countries because its cheap. It's everywhere. You can probably go to a scrap yard, buy a guy a sandwich and he will do it for you. It's not impossible to do with a big torch, a small one is just harder to overheat with. Also any jewelry designer will have one. Or car mechanic.

I am just giving my ideas. Also, you can polish wire. I'm not sure what else you can do with it to change its characteristics.

Mu metal, used in sheets for shielding is very different from tiny thin resistance wire used for, well, resistance. You might as well say that as it's OK to treat ferritic mu metal with hydrogen that it'd be fine to use it on the steel swing arms of a car's suspension. As I say, I'm no metalurgist, and I'd be happy to be proven wrong by a couple of relevant examples, but my engineering Spidey Sense tells me you're on the wrong track.

[zhtoor]

proposed resistor stabilization / aging method:

say the resistor which is to be stabilized is 10K.

apply 100 volts for 5min then 0v for 5min
apply 90 volts for 10min then 0v for 5min
.
.
.
so on....

the time (5min) can be a variable according to the resistance or
a voltage ramp-up followed by a plateau followed by a ramp-down over a period of say a couple of hours.
ie; a programmable heating profile generation waveform for resistor stabilization.

regards and comments required.

[Edwin G. Pettis]

Well, if you really want to mess up an alloy's TCR characteristic, use a torch on it, Manganin will go absolutely crazy as it has a relatively low temperature for messing up the TCR (hence always used at low power and room temperature for precision), even excessive soldering time will cause changes (locally).  Evanohm will tolerate up to about 300°C without major changes, anything over that is going to majorly change its TCR, even under 300°C for sufficiently long will cause modification to the TCR.  The only reliable termination of Evanohm is proper welding and Manganin is almost always soldered but it can be welded to copper of course under the proper conditions.

[Conrad Hoffman]

The thermal conductivity of most resistance alloys is low. My guess, and it's just a guess, is that a brazed connection can be made with little trouble. Obviously one heats the terminal only. With heavier wire you'd probably want a heat block/sink of some sort. IMO, spot welding is better, but I don't know what materials can be reliably spot welded together.

[zhtoor]

i think in case of fine wire joints, it would be very important to consider the amount of energy delivered to the joint in the spot welding process.
an experiment is in order to see what kind of energies could be delivered to the joint for different sizes of manganin wire joints.
some kind of "energy decade box" of capacitors maybe?

regards and thanks again to Mr. Edwin, MisterDiodes, Conrad Hoffman and others.