dc current sensing problem in solar charger

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Hi,

Place a cut.... but leave a solid connection
Click to expand...

I meant one needs a big connection beween those gnd planes. A cut avoids that current of the power side travels to the analog signal side.
Here picture, it says more than thousand words....


Hope it is clear now.

Klaus
 

SunnySkyguy,

Thanks for the detailed reply. The 90 degree concept seems cool! But I don't understand what you mean by 4%/c error. As far as for my knowledge it is 0.39%/C for copper. And for especially designed shunt resistors, it is almost negligible.

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KlausST ,

The picture indeed is worth a thousand words! Thanks a lot.
 

is it necessary to make traces 90 deg when signal is taken from shunt and feed to diff amplifier
 

Depends on coupling factor for stray capacitance, & mutual inductance try pulsing a wire on bench and try to read with scope tip to ground, then do same for breadboard diff amp. But you can work out impedance of noise tolerance of 80 A at 100kHz and higher dv/dt to see what SNR you can tolerate with 75 mV signal. Opposing matched track paths to diff amp will help where CMMR of amp gives out. Also ferrite beads around track pairs will balanced stray fields which is why they call them BALUNS.
 

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