1X or 10X Passive Voltage Probe?

[vze3bbyp]

Hi All,

Suppose you have applied 800kHz, 30ppV sine signal (from a pulse generator) to a 115pF, 10Ohm RC circuit and you want to know the value of the applied voltage as accurate as possible what passive voltage probe would you use, 1X or 10X? Is there a way to check the accuracy of the two measurements? What I do is I use a resistor of known resistance and I divide the current passing through it into the voltage across it measured alternatively with the 1X and the 10X probe. What I see is that throughout one period of the sine wave the 1X probe sustains an R value closer to the known R value than the 10X probe. This makes me conclude, although I'm measuring the voltage across the R and not the voltage across the RC, that the 1X probe is more accurate. Am I right and are there other ways I can objectively check the accuracy of the two probes with regard to measuring the voltage across the RC?

 

[berkeman]

Hi All,

Suppose you have applied 800kHz, 30ppV sine signal (from a pulse generator) to a 115pF, 10Ohm RC circuit and you want to know the value of the applied voltage as accurate as possible what passive voltage probe would you use, 1X or 10X? Is there a way to check the accuracy of the two measurements? What I do is I use a resistor of known resistance and I divide the current passing through it into the voltage across it measured alternatively with the 1X and the 10X probe. What I see is that throughout one period of the sine wave the 1X probe sustains an R value closer to the known R value than the 10X probe. This makes me conclude, although I'm measuring the voltage across the R and not the voltage across the RC, that the 1X probe is more accurate. Am I right and are there other ways I can objectively check the accuracy of the two probes with regard to measuring the voltage across the RC?

Welcome to the PF.

The Tektronix 'scope probe primer should be useful reading for you. It is available at this Tek tutorial page:

http://www.tek.com/learning/oscilloscopes/

You need to register to download it, but the registration is free.