I am trying to do power analysis on my target, which works on 3.3v. Without resistor, the average current while running is about 140mA.
I used a 10Ohm resistor as a shunt resistor with 5V power supply. I connected the shunt resistor between 5V
and target VCC pin, and measure the voltage change between VCC PIN and GND. (decoupling caps have been removed). However oscilloscope did not give a reasonable power consumption line.
Is there any thing wrong in my setup? Any guidance on shunt resistor choosing?
Thank you very much for any help!