When I make a measurement using a scope and observe transducer voltage output on the scope screen, I want to eliminate the noise as much as possible which is due to device and scope coupling or common mode noise like 50 Hz and its harmonics or capacitive coupling ghost voltages. I want to be left with the transducer's own noise(intrinsic) as much as possible.
After reading this question I still am not sure about the common practice.
Is it better to use 3-prong or 2-prong(aka eliminating the earth) in many cases for eliminating ground loops or capacities coupling between the device to be measured and the scope?
Is the only reason to use 3-prong for a scope safety?
In instrumentation should the instrument be powered from an isolation amplifier to eliminate ground loops or coupling noise? Can you provide a diagram which illsutares some good practice?