The uCurrent? is the only commercially available solution to the problem of burden voltage on a multimeter. See the article below to see why this little known problem can be a real big issue, even with your “precision” 0.05% Fluke multimeter. It also turns your multimeter into a powerful and precise nanoamp level measurement tool!

Thousands are in use all around the world, and it has quickly become the industry standard low cost tool for low power current measurement in modern low power microcontroller based digital electronics.

The μCurrent? GOLD is the latest design with greatly improved specs over the original. Improvements have been made in basic accuracy, bandwidth (now you can measure fast changing “sleep” modes), current handling, and an added shorting mode to ensure uninterrupted power to your device under test while changing ranges. The μCurrent can rival 5 1/2 digit multimeters in accuracy, it is truly a precision instrument.

For increased battery life and greater potential output voltage swing, 3 x AAA batteries in series can be used instead of the coin cell. No modifications are required, just wire in parallel with the existing coin cell holder. A 3 x AAA holder fits in the existing box.

https://www.eevblog.com/projects/ucurrent/