On Mon, 02 Apr 2007 01:02:29 +0200, Fred Bartoli
r_AndThisToo wrote:

John Larkin a écrit :
On Sun, 01 Apr 2007 10:44:51 -0700, Jim Thompson
wrote:

On Sun, 01 Apr 2007 19:41:04 +0200, Fred Bartoli
r_AndThisToo wrote:

Jim Thompson a écrit :
Cleaning out desk, found attached.

WhatZit?

...Jim Thompson

Through hole current shunt?
Yep. 6 milli-ohm, NiCr; from the Bosch motor control project ;-)

...Jim Thompson

IRC makes them too, little omegas (appropriate, huh?) made out of
manganin, surface mount. We make our own current shunts for our NMR
amps, punched or edm cut out of sheet manganin,


with tricky top-secret shapes.

Joking or eddy?

There are a number of issues: transient thermoelectrics, eddy current
effects (especially as we need to heat sink them), external 60 Hz mag
field pickup, and a few other practical items. We make current pulses
from 3 amps max to as much as 100 amps max, and need to settle to a
few ppm in, say, 100 microseconds, and stay there for as much as 100
ms... then recover to zero to, say, 1 ppm in another 100 usec.

Vishay makes some very nice, super-accurate 4-lead power resistors in
a TO-3 can. If you apply a current step to them, the voltage
overshoots about 2000 ppm for hundreds of microseconds, mostly from
eddy-current effects.

John