USB noise measurement

Hello , I want to measure the noise of my computer usb 5v , How do i set up my QA401 and how to measure up to 100 khz ?


Hi @fdracing, since the USB supply voltage is 5V, you can go directly into the QA401. The best option would probably be a scope probe in x1 mode, and a USB breakout board, and then connect the ground of the scope probe to the USB ground, and touch the tip to the 5V.

I did just that and measured the USB supply on a QA401 at -53.1 dBV (20 kHz BW, no weighting). This is a hub powered by a 5V wallwart.

Thank you Matt

the usb from my recent computer is not that clean

gonna make some tweaks to clean that out :wink: