During a project, it's very common to test the power consumption of a circuit so we can know how big of a battery we need and how long our circuit can last on a single battery charge. Usually we measure power consumption using the current, but to accurately measure how much current cunsumed, we need some very bulky instrument and device which can cause you a fortune.  

We all know the Ohm Law,

V=IR, 

So, when resistance of a circuit is 1 ohm, I = V.

Therefore, by measuring the voltage across the 1ohm resistor, we can get a sense of how much the power consumption is.

How to do it? you can use a multimeter, but its refreshing rate is too slow to capture some current surge, so, we can use a oscilloscope to measure the voltage drop across the ends of the resistor to calculate the voltage and exstimate the current consumption. Here is the circuit,

After that, here is the reading from the scope,

The gap between the 2 waveforms is the voltage drop = current consumed. 

Job done~