Probing an externally powered circuit using MSP432 connected to the PC
The short answer is Yes. You will need to have the same GND potential for your measurement device and DUT.
But you will need to be careful, as others commented, Since you mentioned power outlet, likely you mean the Mains. for correct measurement, it is not only the ground, but the Earth. when you don't have the same earth, you don't have the same &quot;reference&quot; ground and your measurement can be very wrong and damage your device/instruments.
Depends on the setup and how DUT is made, isolated transformer might be needed.
with your limited info, can't tell.