Maker Pro
Maker Pro

What I learnt this year.

S

Syd Rumpo

Jan 1, 1970
0
Ferrite cores conduct electricity! Ouch! Not brilliantly, but a
measured 10k or so over a cm or so.

I've never been much involved in the black arts of coils, but for the
past half century I've believed/assumed ferrite to be an insulator.
Don't know why.

For some reason, the RM12 cores I'm using have the type printed on one
half of the core only, so mixing up types could happen if you were
careless. I have been. But it seems that the two types I'm using have
quite different resistivities, so I can match up the two halves again.

Cheers
 
J

JW

Jan 1, 1970
0
Ferrite cores conduct electricity! Ouch! Not brilliantly, but a
measured 10k or so over a cm or so.

I've never been much involved in the black arts of coils, but for the
past half century I've believed/assumed ferrite to be an insulator.
Don't know why.

I didn't think it conducts either, or at least had a very high resistance.
<http://www.google.com/url?sa=t&rct=...4ID4Cw&usg=AFQjCNHg99f2du1HUw8liN7kWd1GQlS33g>

Apparently some are and some aren't. I just grabbed a random core I have
lying around, and it's resistance is >100 Megohms which is the limit of my
DMM.
 
B

Bill Sloman

Jan 1, 1970
0
Ferrite cores conduct electricity! Ouch! Not brilliantly, but a measured 10k or so over a cm or so.

I've never been much involved in the black arts of coils, but for the
past half century I've believed/assumed ferrite to be an insulator.
Don't know why.

For some reason, the RM12 cores I'm using have the type printed on one half of the core only, so mixing up types could happen if you were careless.I have been. But it seems that the two types I'm using have quite different resistivities, so I can match up the two halves again.

I've been aware that ferrites were conductive since I first played with them in the late 1960's, and furthermore I knew - from the start - that manganese-zinc ferrites were a lot more conductive - but had higher permeability - than nickel-zinc ferrites.

The old Mullard ferrite data books were horrible in many respects, but theydid spell this out.
 
S

Spehro Pefhany

Jan 1, 1970
0
I've been aware that ferrites were conductive since I first played with the=
m in the late 1960's, and furthermore I knew - from the start - that mangan=
ese-zinc ferrites were a lot more conductive - but had higher permeability =
- than nickel-zinc ferrites.

The old Mullard ferrite data books were horrible in many respects, but they=
did spell this out.

I've never seen it spelled out, but I knew it was true (didn't know it
varied that much). Perhaps that's at least partly why some are coated
with epoxy.


Best regards,
Spehro Pefhany
 
Ferrite cores conduct electricity! Ouch! Not brilliantly, but a
measured 10k or so over a cm or so.

I've never been much involved in the black arts of coils, but for the
past half century I've believed/assumed ferrite to be an insulator.
Don't know why.

For some reason, the RM12 cores I'm using have the type printed on one
half of the core only, so mixing up types could happen if you were
careless. I have been. But it seems that the two types I'm using have
quite different resistivities, so I can match up the two halves again.

I knew it, but got reminded recently when I got a 32kV tingle
from touching a supposedly insulated core!

Cheers,

James arthur
 
S

Syd Rumpo

Jan 1, 1970
0
How did you contact the cores? The size of the contact area can make a lot of
difference.

Oh, just meter probes, good enough for a comparison. These are RM12
cores, so a better way might be to clip them together and use the spring
clips as terminals.
..
..
..
No, not really better - I get about 2k between clips on the RM12 N41
1000nH cores I'm using, and about 7k on an N87 160nH set, but all rather
sensitive to pressure. Still, a clear difference.

I guess conductive epoxy would make a good contact, but I'm not *that*
interested.

Cheers
 
A

Adrian Tuddenham

Jan 1, 1970
0
Syd Rumpo said:
Oh, just meter probes, good enough for a comparison. These are RM12
cores, so a better way might be to clip them together and use the spring
clips as terminals.
.
.
.
No, not really better - I get about 2k between clips on the RM12 N41
1000nH cores I'm using, and about 7k on an N87 160nH set, but all rather
sensitive to pressure. Still, a clear difference.

I guess conductive epoxy would make a good contact, but I'm not *that*
interested.

A four-terminal measurement would eliminate contat resistance from the
measurement - if you ever wanted to go to that much trouble to get a
definitive answer.
 
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