Prev: Buy Designer Handbags
Next: Where is Archimedes Lever??
From: AM on 8 Jul 2010 10:38
On Thu, 08 Jul 2010 07:22:34 -0700, John Larkin
<jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote:

>On Thu, 08 Jul 2010 07:14:10 -0700, AM
><thisthatandtheother(a)beherenow.org> wrote:
>
>> Use the "Z" alloy.
>
>It's expensive and hard to get, and I don't think we could photo-etch
>it.
>
>John


That's what lasers are for. Worst case, send them out to be custom
trimmed.
From: AM on 8 Jul 2010 10:41
On Thu, 08 Jul 2010 10:33:31 -0400, Spehro Pefhany
<speffSNIP(a)interlogDOTyou.knowwhat> wrote:

>On Thu, 08 Jul 2010 07:14:10 -0700, AM
><thisthatandtheother(a)beherenow.org> wrote:
>
>>On Thu, 08 Jul 2010 06:54:49 -0700, John Larkin
>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote:
>>
>>>On Thu, 08 Jul 2010 07:36:08 -0400, JW <none(a)dev.null> wrote:
>>>
>>>>On Wed, 07 Jul 2010 11:40:15 -0700 John Larkin
>>>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in Message id:
>>>><19i936d8s89amglk2ohfdgqei711nga6fg(a)4ax.com>:
>>>>
>>>>>Shunts usually self-heat, which adds a nonlinearity to the power
>>>>>measurement. So it's worth getting ones with a low TC.
>>>>
>>>>Why not use a 4 wire shunt?
>>>
>>>Sure. But that doesn't help the self-heating/TC problem. If you're
>>>working with DC, you can have thermocouple potential problems, too.
>>>
>>>John
>>>
>>>
>>
>> Use the "Z" alloy.
>
>This stuff looks pretty nice:
>http://www.isabellenhuette.de/pdf/WIDER_LEG/ZERANIN-ISABELLENHUETTE-R.pdf
>

My reference was to the previously posted foil resistor vendor specs.

One would have to get pretty fancy to keep inductance low with wire
solutions. Flowery fan folds and such... it works though.
From: John Larkin on 8 Jul 2010 11:56
On Thu, 08 Jul 2010 07:38:02 -0700, AM
<thisthatandtheother(a)beherenow.org> wrote:

>On Thu, 08 Jul 2010 07:22:34 -0700, John Larkin
><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote:
>
>>On Thu, 08 Jul 2010 07:14:10 -0700, AM
>><thisthatandtheother(a)beherenow.org> wrote:
>>
>>> Use the "Z" alloy.
>>
>>It's expensive and hard to get, and I don't think we could photo-etch
>>it.
>>
>>John
>
>
> That's what lasers are for. Worst case, send them out to be custom
>trimmed.

We used to make planar manganin shunts using dies and a punch press,
but that was expensive. We tried CO2 laser machining, but the laser
mostly bounced off (manganin is mostly copper, an excellent IR
reflector) and the edges were awful anyhow. Lately we have them
photo-etched, which works beautifully. I doubt that zeranin can be
laser cut any better; it's very similar to manganin, just uses tin
instead of nickel.

We don't trim our shunts, we just trim gain electronically downstream.

John


From: AM on 8 Jul 2010 12:24
On Thu, 08 Jul 2010 08:56:21 -0700, John Larkin
<jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote:

>On Thu, 08 Jul 2010 07:38:02 -0700, AM
><thisthatandtheother(a)beherenow.org> wrote:
>
>>On Thu, 08 Jul 2010 07:22:34 -0700, John Larkin
>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote:
>>
>>>On Thu, 08 Jul 2010 07:14:10 -0700, AM
>>><thisthatandtheother(a)beherenow.org> wrote:
>>>
>>>> Use the "Z" alloy.
>>>
>>>It's expensive and hard to get, and I don't think we could photo-etch
>>>it.
>>>
>>>John
>>
>>
>> That's what lasers are for. Worst case, send them out to be custom
>>trimmed.
>
>We used to make planar manganin shunts using dies and a punch press,
>but that was expensive. We tried CO2 laser machining, but the laser
>mostly bounced off (manganin is mostly copper, an excellent IR
>reflector) and the edges were awful anyhow. Lately we have them
>photo-etched, which works beautifully. I doubt that zeranin can be
>laser cut any better; it's very similar to manganin, just uses tin
>instead of nickel.
>
>We don't trim our shunts, we just trim gain electronically downstream.
>
>John
>

Get a micro cleaver setup like the chemical/bio labs use to cleave off
pieces of frozen sample media for analysis.
From: whit3rd on 8 Jul 2010 14:29
On Jul 8, 9:24 am, AM <thisthatandtheot...(a)beherenow.org> wrote:
> On Thu, 08 Jul 2010 08:56:21 -0700, John Larkin

> >>  That's what lasers are for.  Worst case, send them out to be custom
> >>trimmed.

> >We used to make planar manganin shunts using dies and a punch press,
> >but that was expensive. We tried CO2 laser machining, but the laser
> >mostly bounced off (manganin is mostly copper, an excellent IR
> >reflector) and the edges were awful anyhow. Lately we have them
> >photo-etched, which works beautifully. ...
> >We don't trim our shunts, we just trim gain electronically downstream.

>  Get a micro cleaver setup like the chemical/bio labs use to cleave off
> pieces of frozen sample media for analysis.

I've seen shunts that were trimmed by holding 'em up to a grinding
wheel.
The problem is, mechanical stress raises the resistance (until heat or
age
anneals the metal). Chemical etching leaves a raw-metal surface,
which
will in time oxidize (changing the resistance). Laser trimming is
fine for SMALL resistors, removing serious metal from a 200A
shunt is a frightening prospect.

Make the shunt, anneal and passivate the surface, then use some
other gain trim downstream.
First  |  Prev  |  Next  |  Last
Pages: 1 2 3 4 5
Prev: Buy Designer Handbags
Next: Where is Archimedes Lever??