I'm developing a device which must be able to measure milliamps and microamps on one of its lines (down to 1 microamp, but also clearly seeing if it's less than 1uA). It's going to be DC of different voltages (0-3.3V), but always fixed when measuring current.
So the total scale is 1uA - 10ma. It doesn't have to be a megaprecision device, there are no fixed specs regarding accuracy (actually, I set them). Besides, I might have a calibration setting in the software, I can build a calibration circuit no problem.
I'm still on the brainstorming stage, some parts of the future device have already their final form, or at least I have a clear idea of how it should work, but most are still not finalized. So everything can be changed. Especially if you propose some good ideas, I'm open to ideas.
I haven't decided what my core MCU is going to be, to be honest, there are options. The project doesn't require much magic, so probably naked Atmega328p programmed in Arduino IDE. No need to make it more complicated than it is. But yeah, there are options, it could also be PIC. And it's not what the question is about.
I decided to use 10 Ohm shunt resistor with two current sense amplifiers attached to it, INA186. The current sense amplifiers have 0.5 NANOamp bias current (DATASHEET), which, I think, is totally tolerable.
So the questions are:
1. Can I get away with the circuit in the picture? How reliable would that circuit be? What problems could I expect with it? What are other options to measure 1uA - 10mA?
2. I feel like staying with jelly bean 10-bit ADC MCUs that I have around me, but if some 12-bit or 14-bit MCU (in my case, PIC) would offer significant advantage in circuit design and/or reliability at little or no extra cost, I would consider that. I have enough free pins on MCU for multiple ADC inputs.
3. Any, as Dave from EEVBlog says, traps for young players?