PXI 5922 Sampling rate and SNR

[Mukeun]

Hello, I'm using PXI-5922 high speed digizer lately.

On the specification it says, for higher sampling rate, the SNR is lower than the lower sampling rate.

For example, at 10V p-p range if the sampling rate is 1MS/s the SNR is 108 dB, and if the sampling rate is 10MS/s, the SNR is 91dB.

I guess that means the noise level goes higher when we use higher sampling rate.

Can somebody explain why this happens?

Why does the device more noise with higher sampling rate?

Thank you.

[garretth]

Hi Mukeun,

When you sample at higher rates with the 5922 your dynamic range decreases. This decrease in vertical resolution introduces more quantization error which in turn causes the signal to spread in the frequency domain. This skirting shows up as more power in the noise floor. So, essentially, it is the decrease of resolution that causes the noise floor to increase.

This document is a good reference on how the 5922 works.

Cheers,