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| Looking for a Probe to Use for 5V DC Power Supply Ripple Measurement |
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| bendras:
I would like to measure voltage ripple of a 5V DC-DC buck converter with at least 1mV Peak-to-Peak precision. As far as I understand the best way to do it is with some kind of high impedance differential probe (please correct me if I am wrong). Could someone recommend a differential probe suitable for this type of measurement? |
| Keysight DanielBogdanoff:
Depending on budget and oscilloscope, a lot of people are using power rail probes for this type of measurement. Something like the our N7020A: https://www.keysight.com/en/pd-2471132-pn-N7020A/power-rail-probe?cc=US&lc=eng It was designed to handle offsets higher than 5V, but the power rail probe has been the go-to for a couple years (at least on the enterprise side). Not sure how helpful it will be for your specific application, but this blog post also talks about making single ended measurements with a differential probe: https://community.keysight.com/community/keysight-blogs/oscilloscopes/blog/2018/04/17/use-your-differential-probe-where-you-never-thought-possible |
| nctnico:
The easiest way is to solder a piece of coax to the board and use a DC blocker and 50 Ohm termination at the oscilloscope. |
| bendras:
--- Quote from: Keysight DanielBogdanoff on May 11, 2018, 09:43:56 pm ---Depending on budget and oscilloscope, a lot of people are using power rail probes for this type of measurement. Something like the our N7020A: https://www.keysight.com/en/pd-2471132-pn-N7020A/power-rail-probe?cc=US&lc=eng It was designed to handle offsets higher than 5V, but the power rail probe has been the go-to for a couple years (at least on the enterprise side). Not sure how helpful it will be for your specific application, but this blog post also talks about making single ended measurements with a differential probe: https://community.keysight.com/community/keysight-blogs/oscilloscopes/blog/2018/04/17/use-your-differential-probe-where-you-never-thought-possible --- End quote --- The suggested probe seems to be suitable for the task but as far as I can tell it is only compatible with Keysight oscilloscopes. Does anybody know of a similar probe compatible with bog standard oscilloscopes or at least the ones with the "TekProbe Level II" interface? --- Quote from: nctnico on May 11, 2018, 10:14:25 pm ---The easiest way is to solder a piece of coax to the board and use a DC blocker and 50 Ohm termination at the oscilloscope. --- End quote --- I have investigated this technique but at 5V it seems to be loading the circuit with a few tens of mA of current draw. That is the reason why I am looking for a way to do differential measurements. |
| precaud:
"Ripple" suggests low-freq AC, so why not just use a 1:1 probe into a 1M Ohm AC coupled scope input? The probe's capacitive loading won't be a problem here. |
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