Accurately Measuring Precision Resistors

[Stewart Pinkerton]

Stewart Pinkerton wrote...

Not simply bifilar. The reversal scheme is called an Aryton-Perry
winding, e.g., as in Ohmite's WN series of wirewound non-inductive
resistors, http://www.ohmite.com/catalog/pdf/whm-wnm.pdf And etc.
It's also made by winding a layer in one direction, adding insulation
and winding the next layer back in the opposite direction, with the
turns crossing every 180 degrees.

An 'Ayrton Perry' winding *is* just a standard bifilar winding, most
easily made by cutting the length of wire you need, folding it in the
middle, and winding carefully from that midpoint to the ends, keeping
the twinned wire flat to ensure that adjacent turns always carry
opposing current.

 

[Winfield Hill]

Stewart Pinkerton wrote...

An 'Ayrton Perry' winding *is* just a standard bifilar winding, most
easily made by cutting the length of wire you need, folding it in the
middle, and winding carefully from that midpoint to the ends, keeping
the twinned wire flat to ensure that adjacent turns always carry
opposing current.

Unless it's wound as I described above, which most machines seem
to do. The bifilar idea may be good for hand-made resistors, but
perhaps not for machines.

Also, a bifilar winding isn't necessarily a low-inductance winding,
that was my point. It may well be, if the end is connected, but
it wouldn't have to be. For example, for very low resistances
multiple parallel wires are helpful, wound all at once and shorted.

 

[Tom MacIntyre]

I'm coming in late here, but I always sort of liked the band Chicago's
assessment of this.

Tom

 

[Rich Grise]

Stewart Pinkerton wrote...

Unless it's wound as I described above, which most machines seem
to do. The bifilar idea may be good for hand-made resistors, but
perhaps not for machines.

Also, a bifilar winding isn't necessarily a low-inductance winding,
that was my point. It may well be, if the end is connected, but
it wouldn't have to be. For example, for very low resistances
multiple parallel wires are helpful, wound all at once and shorted.

Bifilar means to me that the wires stay parallel throughout:

Loop
^
\\ \\ \\ \\ \\_
\_ Leads

But the one I had in mind was more like this:
Loop
^
Lead _/ / / / \ \ \ \_ Lead

I don't know what it's called.

Cheers!
Rich

 

[ehsjr]

Bifilar means to me that the wires stay parallel throughout:

Loop
^
\\ \\ \\ \\ \\_
\_ Leads

But the one I had in mind was more like this:
Loop
^
Lead _/ / / / \ \ \ \_ Lead

I don't know what it's called.

Cheers!
Rich

That's it, exactly. Someone called it "contra-wound" -
but I don't know if that is the proper term. On the toroids
I wind that way, the first half occupies about 40% of
the diameter and the last half occupies another 40%.
Ed

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

Rich Grise wrote: [snip]

Bifilar means to me that the wires stay parallel throughout:

Loop
^
\\ \\ \\ \\ \\_
\_ Leads

But the one I had in mind was more like this:
Loop
^
Lead _/ / / / \ \ \ \_ Lead

I don't know what it's called.

Cheers!
Rich

That's it, exactly. Someone called it "contra-wound" -
but I don't know if that is the proper term. On the toroids
I wind that way, the first half occupies about 40% of
the diameter and the last half occupies another 40%.
Ed

I'm just curious as to why you'd want to use a toroid. The whole idea
of a toroid is to increase the magnetic field containment, so you get
better inductance. Then you go winding it bifilar, to _get_rid_ of the
inductance! This doesn't make sense.

Oh, one other point. This "contra-wound" method can only be used for a
single layer. Anf it looks like the winding has to start at the hairpin
bend of hte halfway point and go outward.

 

[Winfield Hill]

Rich Grise wrote...

Bifilar means to me that the wires stay parallel throughout:

Loop
^
\\ \\ \\ \\ \\_
\_ Leads

Indeed, but my point was that the word "bifilar" does not by itself
imply low inductance, as the bifilar construction below illustrates.

.. ---,
.. ^
.. \\ \\ \\ \\ \\
.. V
.. '---

 

[Rich Grise]

Rich Grise wrote: [snip]

Bifilar means to me that the wires stay parallel throughout:

Loop
^
\\ \\ \\ \\ \\_
\_ Leads

But the one I had in mind was more like this:
Loop
^
Lead _/ / / / \ \ \ \_ Lead

I don't know what it's called.

Cheers!
Rich

That's it, exactly. Someone called it "contra-wound" -
but I don't know if that is the proper term. On the toroids
I wind that way, the first half occupies about 40% of
the diameter and the last half occupies another 40%.
Ed

I'm just curious as to why you'd want to use a toroid. The whole idea
of a toroid is to increase the magnetic field containment, so you get
better inductance. Then you go winding it bifilar, to _get_rid_ of the
inductance! This doesn't make sense.

Oh, one other point. This "contra-wound" method can only be used for a
single layer. Anf it looks like the winding has to start at the hairpin
bend of hte halfway point and go outward.

Yes, that's exactly it. I saw it in a book once.

Cheers!
Rich

 

[ehsjr]

Rich Grise wrote:
[snip]

Bifilar means to me that the wires stay parallel throughout:

Loop
^
\\ \\ \\ \\ \\_
\_ Leads

But the one I had in mind was more like this:
Loop
^
Lead _/ / / / \ \ \ \_ Lead

I don't know what it's called.

Cheers!
Rich

That's it, exactly. Someone called it "contra-wound" -
but I don't know if that is the proper term. On the toroids
I wind that way, the first half occupies about 40% of
the diameter and the last half occupies another 40%.
Ed

I'm just curious as to why you'd want to use a toroid. The whole idea
of a toroid is to increase the magnetic field containment, so you get
better inductance. Then you go winding it bifilar, to _get_rid_ of the
inductance! This doesn't make sense.

First, it is not bifilar. Picture a center tapped coil wound
single layer on a toroid. It is that, except that the second
half is wound in the opposite direction.

And it makes sense. I'll try a diagram.

+------+-----------------+
| | |
| Mosfet |
___ | B
___ +------|<----+ A
| ( | T
| ( L1 | T
| ( | E
+------+ | R
) | Y
) L2 | |
) | |
-----------+------------+----+

L2 isolates the bottom of L1 from the negative rail
on the discharge part of the cycle. On the charge part,
the Xl's cancel out, leaving only the winding R in the
charge path. That allows reduction of the charge time.

Ed

 

[Rich Grise]

Watson A.Name - "Watt Sun, the Dark Remover" wrote:

First, it is not bifilar. Picture a center tapped coil wound single
layer on a toroid. It is that, except that the second half is wound in
the opposite direction.

And it makes sense. I'll try a diagram.

+------+-----------------+
| | |
| Mosfet |
___ | B
___ +------|<----+ A
| ( | T
| ( L1 | T
| ( | E
+------+ | R
) | Y
) L2 | |
) | |
-----------+------------+----+

L2 isolates the bottom of L1 from the negative rail on the discharge
part of the cycle. On the charge part, the Xl's cancel out, leaving only
the winding R in the charge path. That allows reduction of the charge
time.

Yabbut, that's a reset winding. We were talking about noninductive
wirewound resistors.

Cheers!
Rich

 

[ehsjr]

Yabbut, that's a reset winding. We were talking about noninductive
wirewound resistors.

Cheers!
Rich

The point I was making was about *windings*, the direction
they go, the fact that the inductances cancel out (verifying
what you were told from my own experience with coils wound
on toroids), and the fact that they are not bifilar.
I didn't think it necessary to state that the thing wound on
a toroid wasn't intended to be a resistor, figuring that is
obvious. But perhaps not....
Ed

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

The point I was making was about *windings*, the direction
they go, the fact that the inductances cancel out (verifying
what you were told from my own experience with coils wound
on toroids), and the fact that they are not bifilar.
I didn't think it necessary to state that the thing wound on
a toroid wasn't intended to be a resistor, figuring that is
obvious. But perhaps not....
Ed

I can only speak for others, not myself. er, whatever...

Here's a copy of your original post (between the << and >>):

<<

Bifilar means to me that the wires stay parallel throughout:

Loop
^
\\ \\ \\ \\ \\_
\_ Leads

But the one I had in mind was more like this:
Loop
^
Lead _/ / / / \ \ \ \_ Lead

I don't know what it's called.

Cheers!
Rich

That's it, exactly. Someone called it "contra-wound" -
but I don't know if that is the proper term. On the toroids
I wind that way, the first half occupies about 40% of
the diameter and the last half occupies another 40%.
Ed
But earlier, this whole thread was all about cancelling inductance so I
assumed that the point of doing either of these was to cancel out the
inductance.

In my case, I was thinking that the first example, \\ \\ \\.. is the way
they were telling me to wind the turns on the resistor with 2 conductors
paralleled in each turn. Of course this is to cancel out inductance.

Then you talked about contra-wound on a toroid. I assumed this was to
cancel out inductance as was being done previously. I did make a
mistake about yours being bifilar. Sorry.

But to continue, I would like to see the complete circuit with the
MOSFET you drew above. Might make a whole lot more sense.

 

[ehsjr]

I can only speak for others, not myself. er, whatever...

Here's a copy of your original post (between the << and >>):

No! The post you quoted (below) was from Rich, not me.
My reply to it begins with the words "That's it , exactly."

<<


That's it, exactly. Someone called it "contra-wound" -
but I don't know if that is the proper term. On the toroids
I wind that way, the first half occupies about 40% of
the diameter and the last half occupies another 40%.
Ed


But earlier, this whole thread was all about cancelling inductance so I
assumed that the point of doing either of these was to cancel out the
inductance.

In my case, I was thinking that the first example, \\ \\ \\.. is the way
they were telling me to wind the turns on the resistor with 2 conductors
paralleled in each turn. Of course this is to cancel out inductance.

Then you talked about contra-wound on a toroid. I assumed this was to
cancel out inductance as was being done previously. I did make a
mistake about yours being bifilar. Sorry.

But to continue, I would like to see the complete circuit with the
MOSFET you drew above. Might make a whole lot more sense.

You're seeing most of it. Add a 555 circuit to the gate
of the mosfet and you have it. See
http://www.homepower.com/files/desulfator.pdf

I can post pictures of a toroid wound that
way, if it would make things clearer.
Ed

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

No! The post you quoted (below) was from Rich, not me.
My reply to it begins with the words "That's it , exactly."
You're seeing most of it. Add a 555 circuit to the gate
of the mosfet and you have it. See
http://www.homepower.com/files/desulfator.pdf

The desulfator article uses two separate inductors, I don't see how
you're doing it with one.

 

[ehsjr]

Watson A.Name - "Watt Sun, the Dark Remover" wrote:

The desulfator article uses two separate inductors, I don't see how
you're doing it with one.

It is one toroid, but it has two inductors wound on
it, with one continuous piece of wire. Just like
a center-tapped inductor, except (see diagram) L2
is wound in the opposite direction from L1.

I tried to reply to this twice before with an
attached picture. I'm guessing that the attachment
is the cause of the problem. I'll try to post
a picture of it - look for Contra-Wound Toroid.

Ed