Measuring the waveform of the current is important for debugging power converters, and to improve efficiency and reduce EMC radiation of every circuit. High-end oscilloscopes have current probes, but these are very expensive. This little, and cheap, board help those, who cannot afford them.
The board can also be used as an evaluation board for INA199.
There are two assembly version of the circuit. One for unidirectional measurements and the other for bidirectional measurements. The range and offset can be adjusted by adjusting R0, U1 and D2.