uCurrent Virtual Ground

[mchamster]

Good morning!

I'm working on a project (it'll be OSH) with a part of the circuit taking inspiration from Dave's original uCurrent. I've read his writeup and have a question on the virtual ground.

I'm trying to improve the measurement range of the device, up to 3A off a 3.3v power supply. What I've come up with is to change the voltage divider to values of 100k / 10k which will give a virtual ground of 300mv. With the virtual ground of 300mv, I can measure currents up to just under 3A which is fine. If the device under test (@ ~3A) is wired backward, the measurement range will be buggered up, but that just means that ensuring proper polarity is important though it shouldn't fry the circuit.

Are there any other down sides to this arrangement?

I've modeled this in LTSpice and it seems to check out, but I'm new to LTSpice and don't yet trust what I'm seeing.

Thanks!

- Jm

[EEVblog]

No reason you can't use a single ground referenced supply. IIRC the amp senses down to the negative rail.

[kandrey89]

Now if it could measure pA to 3A, that would be something