You’re using an oscilloscope to measure the thermal noise voltage across a resistance R. Internally, the oscilloscope has a parallel input resistance Rin and capacitance C, where the voltage on the capacitor is used to deflect electrons in a cathode ray tube to continuously draw a line on the screen proportional to the voltage over time.
The resistor and oscilloscope are at the same temperature. Is it possible to determine R from the amplitude of the fluctuating voltage shown on the oscilloscope?
Measuring noise and measurement noise
You’re using an oscilloscope to measure the thermal noise voltage across a resistance R. Internally, the oscilloscope has a parallel input resistance Rin and capacitance C, where the voltage on the capacitor is used to deflect electrons in a cathode ray tube to continuously draw a line on the screen proportional to the voltage over time.
The resistor and oscilloscope are at the same temperature. Is it possible to determine R from the amplitude of the fluctuating voltage shown on the oscilloscope?
Yes, if Rin≪R
Yes, if Rin∼R
Yes, if Rin≫R
No