NI USB-6009 and Tek's TDS2024C comparesment

[dzonikeda]

My apologies if this topic has already been discussed, but I searched through forum and manuals and couldn't find anything.

I have a problem with measurements made in parallel with NI USB 6009 and Tek's TDS2024C.

I measured high frequency noise on 10 s window.

I used data logger with 40 kHz frequency logging in parallel with TDS2024C (which achieved 250 Hz on 10s window) and got significantly different results.

On figure in attachment, first signal is from scope screenshot data, and the second islogged data from NI USB 6009.

Can someone explain me why are these results so different?

[crossrulz · Accepted solution]

Different sampling frequencies could easily explain this.  Try running the USB-6009 at the same rate as the scope and see what you get.  I also think the TDS2024C has fewer bits in its ADC, so that could also cause some differences.