I have been assigned to monitor the signals related to TPS61091 boost regulator section. I am particularly keen with respect measuring the ripple on the 3.3 V output voltage. I have Lecroy 20Gs/s oscilloscope.

Until now my search on the internet has yielded the below information.

  1. To use the shortest possible probe length. I have the small ground spring with my probe, so i can use it
  2. Measure voltage right across the source: for this, I am planning to probe the voltage directly across the output capacitor.
  3. Probe settings to 1x: this I picked up from a TI application note. I cannot do this probe settings to 10x, because the probes are fixed 10x ones.

My questions:.

  1. Is point number 3 above still has any work around?
  2. Are there any better practices I have missed out to measure the ripple accurately?

1 Answer 1


Don't worry about the 10x vs 1x probe, you can make good measurements with either.

Here's a technique that I recommend: Wind some bare wire around the barrel and tip of your scope probe to make a "socket" for the probe as shown below. Solder the two ends right across the output capacitor. If you have a diff probe you can try that as well for comparison, but this technique has always worked well for me. Try also comparing with your short spring ground clip and you'll likely note that this method gives a better measurement.

enter image description here

  • \$\begingroup\$ Thank you. Does differential probes carry any benefits for probing ripples? Can you please shed some light? \$\endgroup\$
    – Sonder
    Feb 6, 2020 at 15:59
  • 1
    \$\begingroup\$ A (good) differential probe provides common-mode rejection. Common mode noise can show up on a scope depending on the construction of the scope and probe and the frequency and amplitude of the noise, etc. You can check to see if common mode noise is a problem by connecting the ground and tip of the scope probe to the signal you are measuring and if the resultant trace on the scope isn't flat then you may have a common mode noise issue. \$\endgroup\$
    – John D
    Feb 6, 2020 at 16:33
  • \$\begingroup\$ I could measure the ripple with your guidance. Thank you \$\endgroup\$
    – Sonder
    Feb 10, 2020 at 14:04

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