5 mohm resistor...

J

John Larkin

Guest
https://www.dropbox.com/sh/ha6eyf28soy5p2g/AADnz3bK-yJAoDIIJs9g1LYDa?dl=0

This one is solid metal (manganin?) machined down to trim resistance.

I guess we\'ll fake a Kelvin connection and hope for the best.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon
 
fredag den 13. maj 2022 kl. 01.50.45 UTC+2 skrev John Larkin:
https://www.dropbox.com/sh/ha6eyf28soy5p2g/AADnz3bK-yJAoDIIJs9g1LYDa?dl=0

This one is solid metal (manganin?) machined down to trim resistance.

I guess we\'ll fake a Kelvin connection and hope for the best.
Click to expand...

https://www.analog.com/en/analog-dialogue/articles/optimize-high-current-sensing-accuracy.html
 
John Larkin wrote:

https://www.dropbox.com/sh/ha6eyf28soy5p2g/AADnz3bK-yJAoDIIJs9g1LYDa?dl=0

This one is solid metal (manganin?) machined down to trim resistance.

I guess we\'ll fake a Kelvin connection and hope for the best.
Click to expand...

Why bother if there are ready-made four-terminal devices available at
Mouser? I am happily using its 500uOhm version.

Best regards, Piotr
 
On Thu, 12 May 2022 17:36:02 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

fredag den 13. maj 2022 kl. 01.50.45 UTC+2 skrev John Larkin:
https://www.dropbox.com/sh/ha6eyf28soy5p2g/AADnz3bK-yJAoDIIJs9g1LYDa?dl=0

This one is solid metal (manganin?) machined down to trim resistance.

I guess we\'ll fake a Kelvin connection and hope for the best.

https://www.analog.com/en/analog-dialogue/articles/optimize-high-current-sensing-accuracy.html
Click to expand...

We do want giant pads in big solid copper pours, without thermals, to
heat sink these resistors.

And we can adjust our scalings for any measured systematic error.

5% accuracy would be OK in this application. We could calibrate each
resistor if we wanted to, but it\'s not worth the hassle in this case.

The resistors each drive an INA281, on the +48 bus. We measure the ca
20 amp current from the power supply, and the current into each of the
8 plugin boards.

https://www.dropbox.com/s/gr57bhafemypi63/P940_box_9.jpg?raw=1




--

Anybody can count to one.

- Robert Widlar
 
On Fri, 13 May 2022 10:19:48 +0200, Piotr Wyderski
<bombald@protonmail.com> wrote:

John Larkin wrote:

https://www.dropbox.com/sh/ha6eyf28soy5p2g/AADnz3bK-yJAoDIIJs9g1LYDa?dl=0

This one is solid metal (manganin?) machined down to trim resistance.

I guess we\'ll fake a Kelvin connection and hope for the best.

Why bother if there are ready-made four-terminal devices available at
Mouser? I am happily using its 500uOhm version.

Best regards, Piotr
Click to expand...

We have that part in stock. At about 10 amps per resistor, we need a
part with big pads, for good electrical and thermal behavior.

Pseudo-Kelvin contacts to 2-terminal resistors, or arrays of parallel
resistors, seem to work very well.

https://www.dropbox.com/s/83f2bewe6igvor5/P902B6.jpg?raw=1



--

Anybody can count to one.

- Robert Widlar
 
On Fri, 13 May 2022 09:30:46 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 13 May 2022 10:19:48 +0200, Piotr Wyderski
bombald@protonmail.com> wrote:

John Larkin wrote:

https://www.dropbox.com/sh/ha6eyf28soy5p2g/AADnz3bK-yJAoDIIJs9g1LYDa?dl=0

This one is solid metal (manganin?) machined down to trim resistance.

I guess we\'ll fake a Kelvin connection and hope for the best.

Why bother if there are ready-made four-terminal devices available at
Mouser? I am happily using its 500uOhm version.

Best regards, Piotr


We have that part in stock. At about 10 amps per resistor, we need a
part with big pads, for good electrical and thermal behavior.

Pseudo-Kelvin contacts to 2-terminal resistors, or arrays of parallel
resistors, seem to work very well.

https://www.dropbox.com/s/83f2bewe6igvor5/P902B6.jpg?raw=1
Click to expand...

This ain\'t bad:

https://www.dropbox.com/s/c9qprnlur96usox/5.41_mohm.jpg?raw=1

https://www.dropbox.com/s/juqef50e5chvptx/5.07_mohm.jpg?raw=1

It should be even better on a proper PCB with pseudo-Kelvin
between-the-pads connections.


--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon
 
lørdag den 14. maj 2022 kl. 01.44.41 UTC+2 skrev John Larkin:
On Fri, 13 May 2022 09:30:46 -0700, jla...@highlandsniptechnology.com
wrote:
On Fri, 13 May 2022 10:19:48 +0200, Piotr Wyderski
bom...@protonmail.com> wrote:

John Larkin wrote:

https://www.dropbox.com/sh/ha6eyf28soy5p2g/AADnz3bK-yJAoDIIJs9g1LYDa?dl=0

This one is solid metal (manganin?) machined down to trim resistance.

I guess we\'ll fake a Kelvin connection and hope for the best.

Why bother if there are ready-made four-terminal devices available at
Mouser? I am happily using its 500uOhm version.

Best regards, Piotr


We have that part in stock. At about 10 amps per resistor, we need a
part with big pads, for good electrical and thermal behavior.

Pseudo-Kelvin contacts to 2-terminal resistors, or arrays of parallel
resistors, seem to work very well.

https://www.dropbox.com/s/83f2bewe6igvor5/P902B6.jpg?raw=1
This ain\'t bad:

https://www.dropbox.com/s/c9qprnlur96usox/5.41_mohm.jpg?raw=1

https://www.dropbox.com/s/juqef50e5chvptx/5.07_mohm.jpg?raw=1
Click to expand...

how did you measure it?
 
On Sat, 14 May 2022 02:07:21 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 01.44.41 UTC+2 skrev John Larkin:
On Fri, 13 May 2022 09:30:46 -0700, jla...@highlandsniptechnology.com
wrote:
On Fri, 13 May 2022 10:19:48 +0200, Piotr Wyderski
bom...@protonmail.com> wrote:

John Larkin wrote:

https://www.dropbox.com/sh/ha6eyf28soy5p2g/AADnz3bK-yJAoDIIJs9g1LYDa?dl=0

This one is solid metal (manganin?) machined down to trim resistance.

I guess we\'ll fake a Kelvin connection and hope for the best.

Why bother if there are ready-made four-terminal devices available at
Mouser? I am happily using its 500uOhm version.

Best regards, Piotr


We have that part in stock. At about 10 amps per resistor, we need a
part with big pads, for good electrical and thermal behavior.

Pseudo-Kelvin contacts to 2-terminal resistors, or arrays of parallel
resistors, seem to work very well.

https://www.dropbox.com/s/83f2bewe6igvor5/P902B6.jpg?raw=1
This ain\'t bad:

https://www.dropbox.com/s/c9qprnlur96usox/5.41_mohm.jpg?raw=1

https://www.dropbox.com/s/juqef50e5chvptx/5.07_mohm.jpg?raw=1


how did you measure it?
Click to expand...

Lascar power supply, short-circuit current 1.27 amps, and my Fluke
benchtop DVM probing the two red dots.

It\'s a 1% resistor, and a pseudo-Kelvin connection should get me close
to the resistor tolerance.

I wonder how they connect to them while they are trimming/machining
the 5m value.



--

Anybody can count to one.

- Robert Widlar
 
lørdag den 14. maj 2022 kl. 16.37.13 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 02:07:21 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 01.44.41 UTC+2 skrev John Larkin:
On Fri, 13 May 2022 09:30:46 -0700, jla...@highlandsniptechnology.com
wrote:
On Fri, 13 May 2022 10:19:48 +0200, Piotr Wyderski
bom...@protonmail.com> wrote:

John Larkin wrote:

https://www.dropbox.com/sh/ha6eyf28soy5p2g/AADnz3bK-yJAoDIIJs9g1LYDa?dl=0

This one is solid metal (manganin?) machined down to trim resistance.

I guess we\'ll fake a Kelvin connection and hope for the best.

Why bother if there are ready-made four-terminal devices available at
Mouser? I am happily using its 500uOhm version.

Best regards, Piotr


We have that part in stock. At about 10 amps per resistor, we need a
part with big pads, for good electrical and thermal behavior.

Pseudo-Kelvin contacts to 2-terminal resistors, or arrays of parallel
resistors, seem to work very well.

https://www.dropbox.com/s/83f2bewe6igvor5/P902B6.jpg?raw=1
This ain\'t bad:

https://www.dropbox.com/s/c9qprnlur96usox/5.41_mohm.jpg?raw=1

https://www.dropbox.com/s/juqef50e5chvptx/5.07_mohm.jpg?raw=1


how did you measure it?
Lascar power supply, short-circuit current 1.27 amps, and my Fluke
benchtop DVM probing the two red dots.
Click to expand...

on the second one you could directly get a measurement of the difference
by comparing the voltage on the red dots and on the two \"main\" connections
 
On Sat, 14 May 2022 12:26:56 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 16.37.13 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 02:07:21 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 01.44.41 UTC+2 skrev John Larkin:
On Fri, 13 May 2022 09:30:46 -0700, jla...@highlandsniptechnology.com
wrote:
On Fri, 13 May 2022 10:19:48 +0200, Piotr Wyderski
bom...@protonmail.com> wrote:

John Larkin wrote:

https://www.dropbox.com/sh/ha6eyf28soy5p2g/AADnz3bK-yJAoDIIJs9g1LYDa?dl=0

This one is solid metal (manganin?) machined down to trim resistance.

I guess we\'ll fake a Kelvin connection and hope for the best.

Why bother if there are ready-made four-terminal devices available at
Mouser? I am happily using its 500uOhm version.

Best regards, Piotr


We have that part in stock. At about 10 amps per resistor, we need a
part with big pads, for good electrical and thermal behavior.

Pseudo-Kelvin contacts to 2-terminal resistors, or arrays of parallel
resistors, seem to work very well.

https://www.dropbox.com/s/83f2bewe6igvor5/P902B6.jpg?raw=1
This ain\'t bad:

https://www.dropbox.com/s/c9qprnlur96usox/5.41_mohm.jpg?raw=1

https://www.dropbox.com/s/juqef50e5chvptx/5.07_mohm.jpg?raw=1


how did you measure it?
Lascar power supply, short-circuit current 1.27 amps, and my Fluke
benchtop DVM probing the two red dots.

on the second one you could directly get a measurement of the difference
by comparing the voltage on the red dots and on the two \"main\" connections
Click to expand...

You mean to measure where the end wires are soldered?

The \"1 oz\" copper is about 580 uohms per square, so that would add 2
mohms or so.

I could dremel/xacto a bit better and get more Kelvin-ish.



--

Anybody can count to one.

- Robert Widlar
 
On Sun, 15 May 2022 07:05:20 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Sun, 15 May 2022 05:33:38 -0700 (PDT), Lasse Langwadt Christensen
langwadt@fonz.dk> wrote:

søndag den 15. maj 2022 kl. 07.10.14 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 18:57:40 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

søndag den 15. maj 2022 kl. 03.49.17 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 18:32:07 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

søndag den 15. maj 2022 kl. 02.09.41 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 12:26:56 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 16.37.13 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 02:07:21 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 01.44.41 UTC+2 skrev John Larkin:
On Fri, 13 May 2022 09:30:46 -0700, jla...@highlandsniptechnology.com
wrote:
On Fri, 13 May 2022 10:19:48 +0200, Piotr Wyderski
bom...@protonmail.com> wrote:

John Larkin wrote:

https://www.dropbox.com/sh/ha6eyf28soy5p2g/AADnz3bK-yJAoDIIJs9g1LYDa?dl=0

This one is solid metal (manganin?) machined down to trim resistance.

I guess we\'ll fake a Kelvin connection and hope for the best.

Why bother if there are ready-made four-terminal devices available at
Mouser? I am happily using its 500uOhm version.

Best regards, Piotr


We have that part in stock. At about 10 amps per resistor, we need a
part with big pads, for good electrical and thermal behavior.

Pseudo-Kelvin contacts to 2-terminal resistors, or arrays of parallel
resistors, seem to work very well.

https://www.dropbox.com/s/83f2bewe6igvor5/P902B6.jpg?raw=1
This ain\'t bad:

https://www.dropbox.com/s/c9qprnlur96usox/5.41_mohm.jpg?raw=1

https://www.dropbox.com/s/juqef50e5chvptx/5.07_mohm.jpg?raw=1


how did you measure it?
Lascar power supply, short-circuit current 1.27 amps, and my Fluke
benchtop DVM probing the two red dots.

on the second one you could directly get a measurement of the difference
by comparing the voltage on the red dots and on the two \"main\" connections

You mean to measure where the end wires are soldered?

no, same place as the dots on the first one
Both measurements were on the dots.

compare measurements at red and blue dots
https://imgur.com/a/MqQCWnC

I could do that Monday. The blues will obviously be more voltage drop.

sure, the idea is that it\'ll directly show you how much it actually matters

My first test did that. 5.41 mohms.
Click to expand...

https://www.dropbox.com/s/41hk5leasx1h1ho/5m_3cases.jpg?raw=1

Here are some better measurements.

When I get the actual PCB, with the connections between the pads, it
might be better. At any rate, I can use a 2-terminal 2512 5m resistor
in my gadget, no problems.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon
 
mandag den 16. maj 2022 kl. 19.22.37 UTC+2 skrev John Larkin:
On Sun, 15 May 2022 07:05:20 -0700, jla...@highlandsniptechnology.com
wrote:
On Sun, 15 May 2022 05:33:38 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

søndag den 15. maj 2022 kl. 07.10.14 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 18:57:40 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

søndag den 15. maj 2022 kl. 03.49.17 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 18:32:07 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

søndag den 15. maj 2022 kl. 02.09.41 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 12:26:56 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 16.37.13 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 02:07:21 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 01.44.41 UTC+2 skrev John Larkin:
On Fri, 13 May 2022 09:30:46 -0700, jla...@highlandsniptechnology.com
wrote:
On Fri, 13 May 2022 10:19:48 +0200, Piotr Wyderski
bom...@protonmail.com> wrote:

John Larkin wrote:

https://www.dropbox.com/sh/ha6eyf28soy5p2g/AADnz3bK-yJAoDIIJs9g1LYDa?dl=0

This one is solid metal (manganin?) machined down to trim resistance.

I guess we\'ll fake a Kelvin connection and hope for the best.

Why bother if there are ready-made four-terminal devices available at
Mouser? I am happily using its 500uOhm version.

Best regards, Piotr


We have that part in stock. At about 10 amps per resistor, we need a
part with big pads, for good electrical and thermal behavior.

Pseudo-Kelvin contacts to 2-terminal resistors, or arrays of parallel
resistors, seem to work very well.

https://www.dropbox.com/s/83f2bewe6igvor5/P902B6.jpg?raw=1
This ain\'t bad:

https://www.dropbox.com/s/c9qprnlur96usox/5.41_mohm.jpg?raw=1

https://www.dropbox.com/s/juqef50e5chvptx/5.07_mohm.jpg?raw=1


how did you measure it?
Lascar power supply, short-circuit current 1.27 amps, and my Fluke
benchtop DVM probing the two red dots.

on the second one you could directly get a measurement of the difference
by comparing the voltage on the red dots and on the two \"main\" connections

You mean to measure where the end wires are soldered?

no, same place as the dots on the first one
Both measurements were on the dots.

compare measurements at red and blue dots
https://imgur.com/a/MqQCWnC

I could do that Monday. The blues will obviously be more voltage drop..

sure, the idea is that it\'ll directly show you how much it actually matters

My first test did that. 5.41 mohms.
https://www.dropbox.com/s/41hk5leasx1h1ho/5m_3cases.jpg?raw=1

Here are some better measurements.

When I get the actual PCB, with the connections between the pads, it
might be better. At any rate, I can use a 2-terminal 2512 5m resistor
in my gadget, no problems.
Click to expand...

yeh, 2% off with a 1% resistor and just a bit of thought to the layout isn\'t bad
 
On Mon, 16 May 2022 14:47:57 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

mandag den 16. maj 2022 kl. 19.22.37 UTC+2 skrev John Larkin:
On Sun, 15 May 2022 07:05:20 -0700, jla...@highlandsniptechnology.com
wrote:
On Sun, 15 May 2022 05:33:38 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

søndag den 15. maj 2022 kl. 07.10.14 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 18:57:40 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

søndag den 15. maj 2022 kl. 03.49.17 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 18:32:07 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

søndag den 15. maj 2022 kl. 02.09.41 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 12:26:56 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 16.37.13 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 02:07:21 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 01.44.41 UTC+2 skrev John Larkin:
On Fri, 13 May 2022 09:30:46 -0700, jla...@highlandsniptechnology.com
wrote:
On Fri, 13 May 2022 10:19:48 +0200, Piotr Wyderski
bom...@protonmail.com> wrote:

John Larkin wrote:

https://www.dropbox.com/sh/ha6eyf28soy5p2g/AADnz3bK-yJAoDIIJs9g1LYDa?dl=0

This one is solid metal (manganin?) machined down to trim resistance.

I guess we\'ll fake a Kelvin connection and hope for the best.

Why bother if there are ready-made four-terminal devices available at
Mouser? I am happily using its 500uOhm version.

Best regards, Piotr


We have that part in stock. At about 10 amps per resistor, we need a
part with big pads, for good electrical and thermal behavior.

Pseudo-Kelvin contacts to 2-terminal resistors, or arrays of parallel
resistors, seem to work very well.

https://www.dropbox.com/s/83f2bewe6igvor5/P902B6.jpg?raw=1
This ain\'t bad:

https://www.dropbox.com/s/c9qprnlur96usox/5.41_mohm.jpg?raw=1

https://www.dropbox.com/s/juqef50e5chvptx/5.07_mohm.jpg?raw=1


how did you measure it?
Lascar power supply, short-circuit current 1.27 amps, and my Fluke
benchtop DVM probing the two red dots.

on the second one you could directly get a measurement of the difference
by comparing the voltage on the red dots and on the two \"main\" connections

You mean to measure where the end wires are soldered?

no, same place as the dots on the first one
Both measurements were on the dots.

compare measurements at red and blue dots
https://imgur.com/a/MqQCWnC

I could do that Monday. The blues will obviously be more voltage drop.

sure, the idea is that it\'ll directly show you how much it actually matters

My first test did that. 5.41 mohms.
https://www.dropbox.com/s/41hk5leasx1h1ho/5m_3cases.jpg?raw=1

Here are some better measurements.

When I get the actual PCB, with the connections between the pads, it
might be better. At any rate, I can use a 2-terminal 2512 5m resistor
in my gadget, no problems.

yeh, 2% off with a 1% resistor and just a bit of thought to the layout isn\'t bad
Click to expand...

I calculated that the resistance of the solder, from both 2512 pads to
the PCB copper, is around 15 uohms. Tiny.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon
 
søndag den 15. maj 2022 kl. 02.09.41 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 12:26:56 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 16.37.13 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 02:07:21 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 01.44.41 UTC+2 skrev John Larkin:
On Fri, 13 May 2022 09:30:46 -0700, jla...@highlandsniptechnology.com
wrote:
On Fri, 13 May 2022 10:19:48 +0200, Piotr Wyderski
bom...@protonmail.com> wrote:

John Larkin wrote:

https://www.dropbox.com/sh/ha6eyf28soy5p2g/AADnz3bK-yJAoDIIJs9g1LYDa?dl=0

This one is solid metal (manganin?) machined down to trim resistance.

I guess we\'ll fake a Kelvin connection and hope for the best.

Why bother if there are ready-made four-terminal devices available at
Mouser? I am happily using its 500uOhm version.

Best regards, Piotr


We have that part in stock. At about 10 amps per resistor, we need a
part with big pads, for good electrical and thermal behavior.

Pseudo-Kelvin contacts to 2-terminal resistors, or arrays of parallel
resistors, seem to work very well.

https://www.dropbox.com/s/83f2bewe6igvor5/P902B6.jpg?raw=1
This ain\'t bad:

https://www.dropbox.com/s/c9qprnlur96usox/5.41_mohm.jpg?raw=1

https://www.dropbox.com/s/juqef50e5chvptx/5.07_mohm.jpg?raw=1


how did you measure it?
Lascar power supply, short-circuit current 1.27 amps, and my Fluke
benchtop DVM probing the two red dots.

on the second one you could directly get a measurement of the difference
by comparing the voltage on the red dots and on the two \"main\" connections

You mean to measure where the end wires are soldered?
Click to expand...

no, same place as the dots on the first one
 
On Sat, 14 May 2022 18:32:07 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

søndag den 15. maj 2022 kl. 02.09.41 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 12:26:56 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 16.37.13 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 02:07:21 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 01.44.41 UTC+2 skrev John Larkin:
On Fri, 13 May 2022 09:30:46 -0700, jla...@highlandsniptechnology.com
wrote:
On Fri, 13 May 2022 10:19:48 +0200, Piotr Wyderski
bom...@protonmail.com> wrote:

John Larkin wrote:

https://www.dropbox.com/sh/ha6eyf28soy5p2g/AADnz3bK-yJAoDIIJs9g1LYDa?dl=0

This one is solid metal (manganin?) machined down to trim resistance.

I guess we\'ll fake a Kelvin connection and hope for the best.

Why bother if there are ready-made four-terminal devices available at
Mouser? I am happily using its 500uOhm version.

Best regards, Piotr


We have that part in stock. At about 10 amps per resistor, we need a
part with big pads, for good electrical and thermal behavior.

Pseudo-Kelvin contacts to 2-terminal resistors, or arrays of parallel
resistors, seem to work very well.

https://www.dropbox.com/s/83f2bewe6igvor5/P902B6.jpg?raw=1
This ain\'t bad:

https://www.dropbox.com/s/c9qprnlur96usox/5.41_mohm.jpg?raw=1

https://www.dropbox.com/s/juqef50e5chvptx/5.07_mohm.jpg?raw=1


how did you measure it?
Lascar power supply, short-circuit current 1.27 amps, and my Fluke
benchtop DVM probing the two red dots.

on the second one you could directly get a measurement of the difference
by comparing the voltage on the red dots and on the two \"main\" connections

You mean to measure where the end wires are soldered?

no, same place as the dots on the first one
Click to expand...

Both measurements were on the dots.



--

Anybody can count to one.

- Robert Widlar
 
søndag den 15. maj 2022 kl. 03.49.17 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 18:32:07 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

søndag den 15. maj 2022 kl. 02.09.41 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 12:26:56 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 16.37.13 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 02:07:21 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 01.44.41 UTC+2 skrev John Larkin:
On Fri, 13 May 2022 09:30:46 -0700, jla...@highlandsniptechnology.com
wrote:
On Fri, 13 May 2022 10:19:48 +0200, Piotr Wyderski
bom...@protonmail.com> wrote:

John Larkin wrote:

https://www.dropbox.com/sh/ha6eyf28soy5p2g/AADnz3bK-yJAoDIIJs9g1LYDa?dl=0

This one is solid metal (manganin?) machined down to trim resistance.

I guess we\'ll fake a Kelvin connection and hope for the best..

Why bother if there are ready-made four-terminal devices available at
Mouser? I am happily using its 500uOhm version.

Best regards, Piotr


We have that part in stock. At about 10 amps per resistor, we need a
part with big pads, for good electrical and thermal behavior.

Pseudo-Kelvin contacts to 2-terminal resistors, or arrays of parallel
resistors, seem to work very well.

https://www.dropbox.com/s/83f2bewe6igvor5/P902B6.jpg?raw=1
This ain\'t bad:

https://www.dropbox.com/s/c9qprnlur96usox/5.41_mohm.jpg?raw=1

https://www.dropbox.com/s/juqef50e5chvptx/5.07_mohm.jpg?raw=1


how did you measure it?
Lascar power supply, short-circuit current 1.27 amps, and my Fluke
benchtop DVM probing the two red dots.

on the second one you could directly get a measurement of the difference
by comparing the voltage on the red dots and on the two \"main\" connections

You mean to measure where the end wires are soldered?

no, same place as the dots on the first one
Both measurements were on the dots.
Click to expand...

compare measurements at red and blue dots
https://imgur.com/a/MqQCWnC
 
On Sat, 14 May 2022 18:57:40 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

søndag den 15. maj 2022 kl. 03.49.17 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 18:32:07 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

søndag den 15. maj 2022 kl. 02.09.41 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 12:26:56 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 16.37.13 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 02:07:21 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 01.44.41 UTC+2 skrev John Larkin:
On Fri, 13 May 2022 09:30:46 -0700, jla...@highlandsniptechnology.com
wrote:
On Fri, 13 May 2022 10:19:48 +0200, Piotr Wyderski
bom...@protonmail.com> wrote:

John Larkin wrote:

https://www.dropbox.com/sh/ha6eyf28soy5p2g/AADnz3bK-yJAoDIIJs9g1LYDa?dl=0

This one is solid metal (manganin?) machined down to trim resistance.

I guess we\'ll fake a Kelvin connection and hope for the best.

Why bother if there are ready-made four-terminal devices available at
Mouser? I am happily using its 500uOhm version.

Best regards, Piotr


We have that part in stock. At about 10 amps per resistor, we need a
part with big pads, for good electrical and thermal behavior.

Pseudo-Kelvin contacts to 2-terminal resistors, or arrays of parallel
resistors, seem to work very well.

https://www.dropbox.com/s/83f2bewe6igvor5/P902B6.jpg?raw=1
This ain\'t bad:

https://www.dropbox.com/s/c9qprnlur96usox/5.41_mohm.jpg?raw=1

https://www.dropbox.com/s/juqef50e5chvptx/5.07_mohm.jpg?raw=1


how did you measure it?
Lascar power supply, short-circuit current 1.27 amps, and my Fluke
benchtop DVM probing the two red dots.

on the second one you could directly get a measurement of the difference
by comparing the voltage on the red dots and on the two \"main\" connections

You mean to measure where the end wires are soldered?

no, same place as the dots on the first one
Both measurements were on the dots.

compare measurements at red and blue dots
https://imgur.com/a/MqQCWnC
Click to expand...

I could do that Monday. The blues will obviously be more voltage drop.



--

Anybody can count to one.

- Robert Widlar
 
søndag den 15. maj 2022 kl. 07.10.14 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 18:57:40 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

søndag den 15. maj 2022 kl. 03.49.17 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 18:32:07 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

søndag den 15. maj 2022 kl. 02.09.41 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 12:26:56 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 16.37.13 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 02:07:21 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 01.44.41 UTC+2 skrev John Larkin:
On Fri, 13 May 2022 09:30:46 -0700, jla...@highlandsniptechnology.com
wrote:
On Fri, 13 May 2022 10:19:48 +0200, Piotr Wyderski
bom...@protonmail.com> wrote:

John Larkin wrote:

https://www.dropbox.com/sh/ha6eyf28soy5p2g/AADnz3bK-yJAoDIIJs9g1LYDa?dl=0

This one is solid metal (manganin?) machined down to trim resistance.

I guess we\'ll fake a Kelvin connection and hope for the best.

Why bother if there are ready-made four-terminal devices available at
Mouser? I am happily using its 500uOhm version.

Best regards, Piotr


We have that part in stock. At about 10 amps per resistor, we need a
part with big pads, for good electrical and thermal behavior..

Pseudo-Kelvin contacts to 2-terminal resistors, or arrays of parallel
resistors, seem to work very well.

https://www.dropbox.com/s/83f2bewe6igvor5/P902B6.jpg?raw=1
This ain\'t bad:

https://www.dropbox.com/s/c9qprnlur96usox/5.41_mohm.jpg?raw=1

https://www.dropbox.com/s/juqef50e5chvptx/5.07_mohm.jpg?raw=1


how did you measure it?
Lascar power supply, short-circuit current 1.27 amps, and my Fluke
benchtop DVM probing the two red dots.

on the second one you could directly get a measurement of the difference
by comparing the voltage on the red dots and on the two \"main\" connections

You mean to measure where the end wires are soldered?

no, same place as the dots on the first one
Both measurements were on the dots.

compare measurements at red and blue dots
https://imgur.com/a/MqQCWnC

I could do that Monday. The blues will obviously be more voltage drop.
Click to expand...

sure, the idea is that it\'ll directly show you how much it actually matters
 
On Sun, 15 May 2022 05:33:38 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

søndag den 15. maj 2022 kl. 07.10.14 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 18:57:40 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

søndag den 15. maj 2022 kl. 03.49.17 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 18:32:07 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

søndag den 15. maj 2022 kl. 02.09.41 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 12:26:56 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 16.37.13 UTC+2 skrev jla...@highlandsniptechnology.com:
On Sat, 14 May 2022 02:07:21 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

lørdag den 14. maj 2022 kl. 01.44.41 UTC+2 skrev John Larkin:
On Fri, 13 May 2022 09:30:46 -0700, jla...@highlandsniptechnology.com
wrote:
On Fri, 13 May 2022 10:19:48 +0200, Piotr Wyderski
bom...@protonmail.com> wrote:

John Larkin wrote:

https://www.dropbox.com/sh/ha6eyf28soy5p2g/AADnz3bK-yJAoDIIJs9g1LYDa?dl=0

This one is solid metal (manganin?) machined down to trim resistance.

I guess we\'ll fake a Kelvin connection and hope for the best.

Why bother if there are ready-made four-terminal devices available at
Mouser? I am happily using its 500uOhm version.

Best regards, Piotr


We have that part in stock. At about 10 amps per resistor, we need a
part with big pads, for good electrical and thermal behavior.

Pseudo-Kelvin contacts to 2-terminal resistors, or arrays of parallel
resistors, seem to work very well.

https://www.dropbox.com/s/83f2bewe6igvor5/P902B6.jpg?raw=1
This ain\'t bad:

https://www.dropbox.com/s/c9qprnlur96usox/5.41_mohm.jpg?raw=1

https://www.dropbox.com/s/juqef50e5chvptx/5.07_mohm.jpg?raw=1


how did you measure it?
Lascar power supply, short-circuit current 1.27 amps, and my Fluke
benchtop DVM probing the two red dots.

on the second one you could directly get a measurement of the difference
by comparing the voltage on the red dots and on the two \"main\" connections

You mean to measure where the end wires are soldered?

no, same place as the dots on the first one
Both measurements were on the dots.

compare measurements at red and blue dots
https://imgur.com/a/MqQCWnC

I could do that Monday. The blues will obviously be more voltage drop.

sure, the idea is that it\'ll directly show you how much it actually matters
Click to expand...

My first test did that. 5.41 mohms.



--

Anybody can count to one.

- Robert Widlar
 
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