Small carbon composition resistors

[Spehro Pefhany]

Hi, all:-

Does anyone stock relatively low value (eg. 5 to 10 ohm) through-hole
carbon composition resistors that are very small (eg. 0.1W rating)??

They have to be carbon composition for this application.

 

[Joerg]

Hi, all:-

Does anyone stock relatively low value (eg. 5 to 10 ohm) through-hole
carbon composition resistors that are very small (eg. 0.1W rating)??

They have to be carbon composition for this application.

100mW thru-hole in carbon? Not much of a chance in North America, I
guess you'll have to inquire in China. They still do a lot of thru-hole.

 

[Spehro Pefhany]

"> Why comps? At those values, carbon or metal films will be about as

Maybe he's using them as temperature sensors? This might expalin the
desire for small size. Carbon comps are also non-magnetic.

More like heat loss sensors.

They have a couple of other advantages over "modern" parts- surge
capability, and if you need extra noise, maybe for helping oscillators
to start..

I think we buy 1/4 watt ones from digikey. (Ohmite 'little demon')
George H.

Trying for something with less surface area. I might be able to use
BJTs.

 

[Archimedes' Lever]

Back in "the day" I specifically remember carbon comp 1/8 watt in all the
standard values from 0.5 ohm to 22M, but I haven't seen any in the better
part of 40 years.

Jim

The closest one can come is likely the composition glass bodied style
mil spec jobs,that were like 1%. They were the "precision resistor"
before metal film.

 

[Spehro Pefhany]

Sure, but they were rather inductive.

Depends on how they were wound... for example an number of Chaperon
sections connected in series.



Best regards,
Spehro Pefhany

 

[Rich Grise]

Sure, but they were rather inductive.

Not if they were wound right. There's a simple way of doing this - make
a hairpin loop in the middle of the wire, then wind the two ends in
opposite directions.

Cheers!
Rich

 

[Spehro Pefhany]

Not if they were wound right. There's a simple way of doing this - make
a hairpin loop in the middle of the wire, then wind the two ends in
opposite directions.

Cheers!
Rich

How about the distributed capacitance doing it that way? ;-)

 

[Archimedes' Lever]

The real precision resistors were wirewounds. You could buy 0.01%, 5
PPM wirewounds in 1940.

John

Nobody said a damned thing about precision resistors. We are talking
about composition. His 0.5 ohm as well as any values above 2M Ohm are
UNcommon.

 

[Mycelium]

Not if they were wound right. There's a simple way of doing this - make
a hairpin loop in the middle of the wire, then wind the two ends in
opposite directions.

Which yields two series connected inductors.

The winding method is a bit more complicated than that.

 

[Spehro Pefhany]

Strange. Google gives me 15,300 hits, most of which look relevant.

Like this:

http://books.google.com/books?id=kW...m=10#v=onepage&q=Ayrton-Perry winding&f=false

John

Seems a bit confusing.. in some references, that's called
"Ayerton-Mather" (parallel inductive sections, one wound over the
other) from their original 1892 paper.

"Ayerton-Perry" appears to refer (also?) to a construction of variable
inductor that is essentially an Ayerton-Mather winding but where you
can rotate one of the windings relative to the other (so
Ayerton-Mather is the degenerate form of Ayerton-Perry?). It was
described in their 1895 paper.

http://physics.unl.edu/history/histinstr/induction.html
http://physics.unl.edu/history/histinstr/induction_pix/10090.jpg

http://en.wikipedia.org/wiki/William_Edward_Ayrton

All this stuff was done in relation to work on ballistic galvos, early
forms of AC bridges.




Best regards,
Spehro Pefhany

 

[Fred Abse]

Caddock makes some thick-film axial resistors that you can plug into a 50
ohm SMA female and make into a 500 or 1K ohm passive scope probe, good to
5 GHz or so. They use a tricky serpentine pattern on a ceramic tube.

Part numbers, John?

Can't find 'em on Caddock site.

 

[John Larkin]

Part numbers, John?

Can't find 'em on Caddock site.

Here's the Agilent probe that uses them:

http://www.home.agilent.com/agilent...IN&lc=eng&ckey=1210550&cname=AGILENT_EDITORIA

They use the Caddock MG series, 450 or 950 ohms. I could look up the
exact part numbers on Tuesday when I'm back at work. The resistors
work great all by themselves, saving about $2490.

John

 

[John Larkin]

Here's the Agilent probe that uses them:

http://www.home.agilent.com/agilent...IN&lc=eng&ckey=1210550&cname=AGILENT_EDITORIA

They use the Caddock MG series, 450 or 950 ohms. I could look up the
exact part numbers on Tuesday when I'm back at work. The resistors
work great all by themselves, saving about $2490.

John

Sorry. The Agilent link is

http://cp.literature.agilent.com/litweb/pdf/54006-90002.pdf

John