2
\$\begingroup\$

I am trying to measure the noise at the output of my buck regulator. I am getting some ripples. I feel that the ground loop caused by my oscilloscope GND ref might have a small impact here.

I was thinking of approaching this via the tip-barrel approach. Now, I wanted to know if I need specialised probes for the TIP-Barrel approach.

Tip pic.

Now, the probe has a met section shown in the image above. Is that GND? If yes, in the tip-barrel approach, is it ok if I just connect a wire from here to my GND reference in the PCB?

This is shown in the image below. Will just a piece of wire from here to my PCB act as a GND?

Tip-Barrel

\$\endgroup\$
  • 3
    \$\begingroup\$ You might be interested in a watching a few recognized professionals talk about these things: youtu.be/2vzvWUqUtb8?t=504 \$\endgroup\$ – PlasmaHH Mar 7 '16 at 16:25
4
\$\begingroup\$

Yes, that metal section of your probe is ground, and yes, minimizing loop area when probing fast signals is good.

If you're probe didn't come with one of those nice little ground springs as shown in the second picture, yes, you can build a makeshift one with a small piece of wire. Keep the wire as short as possible, and keep the distance between the point you are probing and ground as close as possible i.e. ground the probe to the closest ground on the board.

Edit:

I went hunting for ground springs, since I realized that I actually had no idea if you could buy them. The most common term is "ground spring", or sometimes "short ground clip", and individual replacements can typically be found by searching " ground spring" or similar. For instance, Digikey has the following (among others):

\$\endgroup\$
  • \$\begingroup\$ and where do i connect the normal gnd connection \$\endgroup\$ – Board-Man Mar 7 '16 at 17:18
  • \$\begingroup\$ That spring is your ground connection, remove the ground clip from the probe (on almost all probes, the clip can simply be pulled off). \$\endgroup\$ – uint128_t Mar 7 '16 at 17:20
3
\$\begingroup\$

Yes, it will work as you expect, and is a proper and accepted way for measuring high-frequency signals in a noisy environment.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.