To enable improved accuracy of MetaShunt V2, it would be nice to be able to calibrate at each of the 8 gain stages. With this in mind, I developed a high dynamic range current supply. To test the concept before ordering a custom PCB, I developed an equivalent breadboard version with the first 5 gain stages, seen below. The actual design has isolated power and isolated communications, so it can be connected to the same USB hub as MetaShunt without issue. This prototype however is not isolated, and so was powered by an external USB battery pack. An Adalogger M0 is used to control the gain stages, changing them every few seconds while I record the measured current on MetaShunt V2.

I measured all of the relevant resistors and voltage reference in this design, and calculated the sourced current. Then I measured the current with MetaShunt V2 and compared the difference. The real design will use highly accurate components (0.1% resistors, 0.2% voltage reference, etc.) but for this test I am just measuring the components with a multimeter (accuracy unknown).

So overall, fantastic accuracy across the board, and proved out the concept! Next step is to build the full system and build automatic calibration software for MetaShunt to improve it's accuracy even further. Nonetheless, even without calibration, MetaShunt is currently within 1% of the true current across 5 orders of magnitude in this testing!