10 ohm 1W 0.1% resistor

Maybe. It might not work!

Oh well I thought this was sci.electronics.design not sci.electronics.copy.old.shit. If I wanted to copy and paste I'd write JavaScript.

If I fail I'll concede my place in the contest I'll probably survive somehow

Right, I have other ways to measure the load.

Oh, you can trust your mother, but never trust your ground. :^) My sense R is right next door to my opamp. With non-inverting input and bottom of R into a nice ground plane on the bottom of the pcb.

George H.

[snip]

I used a Kelvin sense resistor for my Bosch motor controller. It was in the milli-Ohm range, looked like a strip of Nichrome, with staggered connections to give a nice Kelvin connection. I posted a photo of it in the past, but now can't find my way back to it :-( ...Jim Thompson

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     Thinking outside the box... producing elegant solutions. 

"It is not in doing what you like, but in liking what you do that 
is the secret of happiness."  -James Barrie

The highside monitors (you know, op amp, FET, pair of resistors) do a true division of the current, so the resistor ratio has to be constant, but not the resistor values; 1% resistors, especially if you can get an array, will track well enough, and the emitter resistor (low current) is the only one that needs to be super low tolerance.

This family in a 5 ohm/995 ohm dual would work, with a heat spreader. A quad suitably wired would present 2.5 ohms to the 300mA current, and that wouldn't require heatsinking. Dunno about prices, though....

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** Just keep the copper traces that supply current to the sense resistor separate from the ones that feed voltage to your measuring circuit.

IOW, have them only meet at the resistor's mounting pads.

... Phil

if you pick off the voltage from the inner edges of the pads you should only see the solder resistance in addition to the resistor.

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