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tech / sci.electronics.design / Re: 5 mohm resistor

SubjectAuthor
* 5 mohm resistorJohn Larkin
+* Re: 5 mohm resistorLasse Langwadt Christensen
|`- Re: 5 mohm resistorjlarkin
`* Re: 5 mohm resistorPiotr Wyderski
 `* Re: 5 mohm resistorjlarkin
  `* Re: 5 mohm resistorJohn Larkin
   `* Re: 5 mohm resistorLasse Langwadt Christensen
    `* Re: 5 mohm resistorjlarkin
     `* Re: 5 mohm resistorLasse Langwadt Christensen
      `* Re: 5 mohm resistorjlarkin
       `* Re: 5 mohm resistorLasse Langwadt Christensen
        `* Re: 5 mohm resistorjlarkin
         `* Re: 5 mohm resistorLasse Langwadt Christensen
          `* Re: 5 mohm resistorjlarkin
           `* Re: 5 mohm resistorLasse Langwadt Christensen
            `* Re: 5 mohm resistorjlarkin
             `* Re: 5 mohm resistorJohn Larkin
              `* Re: 5 mohm resistorLasse Langwadt Christensen
               `- Re: 5 mohm resistorJohn Larkin

1
5 mohm resistor

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Subject: 5 mohm resistor
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 by: John Larkin - Thu, 12 May 2022 23:50 UTC

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

Re: 5 mohm resistor

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Subject: Re: 5 mohm resistor
From: langw...@fonz.dk (Lasse Langwadt Christensen)
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 by: Lasse Langwadt Chris - Fri, 13 May 2022 00:36 UTC

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

Re: 5 mohm resistor

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From: bomb...@protonmail.com (Piotr Wyderski)
Newsgroups: sci.electronics.design
Subject: Re: 5 mohm resistor
Date: Fri, 13 May 2022 10:19:48 +0200
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 by: Piotr Wyderski - Fri, 13 May 2022 08:19 UTC

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

Re: 5 mohm resistor

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From: jlar...@highlandsniptechnology.com
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Subject: Re: 5 mohm resistor
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 by: jlar...@highlandsniptechnology.com - Fri, 13 May 2022 14:38 UTC

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
>

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

Re: 5 mohm resistor

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Subject: Re: 5 mohm resistor
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 by: jlar...@highlandsniptechnology.com - Fri, 13 May 2022 16:30 UTC

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

--

Anybody can count to one.

- Robert Widlar

Re: 5 mohm resistor

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Subject: Re: 5 mohm resistor
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 by: John Larkin - Fri, 13 May 2022 23:44 UTC

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

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

Re: 5 mohm resistor

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Subject: Re: 5 mohm resistor
From: langw...@fonz.dk (Lasse Langwadt Christensen)
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 by: Lasse Langwadt Chris - Sat, 14 May 2022 09:07 UTC

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?

Re: 5 mohm resistor

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Subject: Re: 5 mohm resistor
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 by: jlar...@highlandsniptechnology.com - Sat, 14 May 2022 14:37 UTC

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?

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

Re: 5 mohm resistor

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Subject: Re: 5 mohm resistor
From: langw...@fonz.dk (Lasse Langwadt Christensen)
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 by: Lasse Langwadt Chris - Sat, 14 May 2022 19:26 UTC

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

Re: 5 mohm resistor

<hlg08hpcd7v5o6ds3ms29v0ulo1101fv6u@4ax.com>

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Subject: Re: 5 mohm resistor
Date: Sat, 14 May 2022 17:09:31 -0700
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 by: jlar...@highlandsniptechnology.com - Sun, 15 May 2022 00:09 UTC

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
>

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

Re: 5 mohm resistor

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Subject: Re: 5 mohm resistor
From: langw...@fonz.dk (Lasse Langwadt Christensen)
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 by: Lasse Langwadt Chris - Sun, 15 May 2022 01:32 UTC

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

Re: 5 mohm resistor

<pvm08hp390ph5kpf78gnamodf0m5cliv8t@4ax.com>

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 by: jlar...@highlandsniptechnology.com - Sun, 15 May 2022 01:49 UTC

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

Both measurements were on the dots.

--

Anybody can count to one.

- Robert Widlar

Re: 5 mohm resistor

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Subject: Re: 5 mohm resistor
From: langw...@fonz.dk (Lasse Langwadt Christensen)
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 by: Lasse Langwadt Chris - Sun, 15 May 2022 01:57 UTC

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

Re: 5 mohm resistor

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 by: jlar...@highlandsniptechnology.com - Sun, 15 May 2022 05:10 UTC

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
>

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

--

Anybody can count to one.

- Robert Widlar

Re: 5 mohm resistor

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Subject: Re: 5 mohm resistor
From: langw...@fonz.dk (Lasse Langwadt Christensen)
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 by: Lasse Langwadt Chris - Sun, 15 May 2022 12:33 UTC

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

Re: 5 mohm resistor

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 by: jlar...@highlandsniptechnology.com - Sun, 15 May 2022 14:05 UTC

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.

--

Anybody can count to one.

- Robert Widlar

Re: 5 mohm resistor

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From: jlar...@highland_atwork_technology.com (John Larkin)
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Subject: Re: 5 mohm resistor
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 by: John Larkin - Mon, 16 May 2022 17:22 UTC

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.

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

Re: 5 mohm resistor

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Subject: Re: 5 mohm resistor
From: langw...@fonz.dk (Lasse Langwadt Christensen)
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 by: Lasse Langwadt Chris - Mon, 16 May 2022 21:47 UTC

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

Re: 5 mohm resistor

<a8j58hdcdp49i7vjpgnkqiu7aik8jjjbjh@4ax.com>

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Subject: Re: 5 mohm resistor
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 by: John Larkin - Mon, 16 May 2022 22:17 UTC

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

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

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