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From: Capt. Cave Man on 8 Jul 2010 09:15
On Thu, 08 Jul 2010 22:41:13 +1000, Grant <omg(a)grrr.id.au> wrote:

>On Wed, 07 Jul 2010 07:39:37 -0700, Capt. Cave Man <ItIsSoEasyACaveManCanDoIt(a)upyers.org> wrote:
>
>>On Wed, 07 Jul 2010 18:54:39 +1000, Grant <omg(a)grrr.id.au> wrote:
>>
>>>On Wed, 07 Jul 2010 09:20:18 +0200, Fred Bartoli <myname_with_a_dot_inbetween(a)free.fr> wrote:
>>>
>>>...
>>>>I'm designing an energy metering ammeter and am looking after a
>>>>0.1/0.2R, preferably SMT, shunt.
>>>>
>>>>On the average all of them will sum up to half a billion euro energy, so
>>>>it has to be accurate :-)
>>>>
>>>>It'll work in some harsh environment and must :
>>>>* work @ 85�C Tamb, (100�C PCB temp)
>>>>* be low tempco (preferably lower than 20ppm/K)
>>>>* real low aging for less than yearly calibration
>>>>* preferably high initial accuracy to hopefully bypass one calibration step
>>>
>>>1%, 0.1% better?
>>>>
>>>>
>>>>None of the usual suspects fit the bill.
>>>>
>>>>Any manufacturer / part series to suggest?
>>>
>>>Only thing I've found for accurate shunts better than 1% is lots of 0.1%
>>>resistors in parallel.
>>>
>>>But I use axial lead or SMD big enough to hand solder. .1, .2R is high
>>>value for a shunt anyway?
>>>
>>>0.1% 250mW 15ppm start at 10R, 5 or 10 in parallel too silly?
>>>
>>>Grant.
>>
>> Precision current shunts are readily available at 0.1% ratings.
>> They have to be trimmed to that level of precision.
>>
>> It is also very easy to perform said trimming for accuracy, so why
>>would they not make them that accurate?
>>
>> Answer: They don't.
>>
>> They, in fact do make precision shunts and using paralleled banks is
>>pretty damned silly.
>
>Not on my budget ;) But I'm not designing for production, prototyping.
>
>Grant.

There are military surplus stores around and many times industrial
liquidators.

You could find what is needed to make a bank at such a place. Ebay too
has parts sections and people run whole stores there now.
From: Uwe Hercksen on 9 Jul 2010 08:59


Fred Bartoli schrieb:

> I'm designing an energy metering ammeter and am looking after a
> 0.1/0.2R, preferably SMT, shunt.
>
Hello,

look here:
http://www.isabellenhuette.de/en/lowohmresistors/resistor/baureihe/3/?no_cache=1

Precision resistors for energy metering, but with 0.1 Milliohm and less.

Do you want 0.1/0.2 Ohm or 0.1/0.2 Milliohm?

Here are also the 100 Milliohm:
http://www.isabellenhuette.de/pdf/PASSIV/SMR.pdf

Au revoir

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