PXI-5922 Noise Floor and Resolution

[ivanperino]

I am looking for an explanation. I am not able to understand it by my self.

When looking at the Noise Density of the PXI-5922 (Figure 7 of Specifications), the vertical axis is dBFS/Hz. The dBFS unit could be converted to V as follows: V = FS*10^(dBFS/20) with FS being 1V if using the board in 2Vpp range. Is this correct?  However, it would not be power spectral density given the V should be squared. Is this Amplitud Spectral Density or something alike? For power Spectral Density I would expect to see dBm/Hz or V^2/Hz or even V/sqrt(Hz).

In short. If using the 2Vpp range. Can anyone tell how to convert dBFS/Hz to V^2/Hz or to dBm/Hz ?

Thank you very much in advance

iP 

[kvannorsdel@draper.com]

This is funny.  I have the EXACT same question about the EXACT same instrument!   DId you ever get an answer?

[Henrik_Volkers]

If you take a look into the calibration manual the calibration specs are RMS values ..(>100 Hz )

If you already have a 5922  you should measure the actual noise in your setup, since type of PXI-chassis, powersupply, slot position and surrounding cards can and will have an influence. Next would be to measure noise with your actual cabling (terminated by same impedances (incl. ground) than your actual sources) and your actual aquisition configuration 😉

[kvannorsdel@draper.com]

Hi Henrik,

Greetings back to you and thank you for your response!  I will dig up the cal manual and see if that indeed helps.  Thank you again.