We use these guys where I work. Cheap, can easily do 100s of amps, 1% accuracy, no heat problems, has 4 terminals built in.
We used to use that kind of material, but the voltage offset (‘thermal EMF’) of that material is too great. From having the two ends at different temperatures. From track heating …
There’s no separate voltmeter as such. The CSR’s feed straight back to the dedicated chip that runs the display, through a multiplexer. But I bet you are right about the reason they’ve used a CSR that is a multiple of ten. And they probably figured 0R01 was too low.
But as I’ve said the display only reads to the nearest 100mA anyway. So with only (say) a 120mV drop as you would get from a 0R05 CSR you would still have way more resolution from an 8 bit ADC than required. Heck, even if the display could cope with from 0-10A (which is more than the unit can output) that would only be 100 values.
Curious. Well, you know your application better than I do. I’m a little surprised that the difference in temperature could be high enough to be relevant. Aren’t thermal EMF coefficients in the realm of microvolts /K (whereas the voltage drop across the shunt should be in millivolts)? Seems like not a big deal unless you’ve got like a 100 C difference. You can’t use a ground plane or something to smooth out the temperature difference?
I’ve always wondered about that. I’d like to test the same device with a 4 layer board, but that’s not my decision.
Ahh, yeah, you’ve got fewer options on a 2-layer board. Still… I can imagine some solutions, like tightly interwoven “combs” of traces. They can be at a bare minimum spacing, since the voltage difference is tiny. Might even be possible to glue a heatspreader on top if you’re confident in the soldermask layer.