They are all ways you can make oscilloscope probes that measure current. If you think of a scope as a voltage measurement device, you ought to watch the recent video from Keysight Technology (see ...

[Paul] knew that he could get an oscilloscope that would measure the microamp signals ... He’s trying to visualize what’s going on with the current draw of a microcontroller at various points ...

Current is a measure of how much electric charge flows through a circuit. The more charge that flows, the bigger the current. Current is measured in amperes. The symbol for ampere is A.