Current Probe Deskew Question  - Page 1
Forum section: electronics / testgear

author: TomKatt
author_rank: Frequent Contributor
timestamp: June 08, 2024, 12:26:49 am
content: So I’m just learning about current probe Deskew fixtures…. Is this something that you should measure every time you use the same set of probes, or once you measure the skew with a specific set of probes is that somewhat of a constant latency? In other words, if I got access to a Deskew fixture and measured the skew time for my current probe, would that latency time be constant so I could apply it the next time I used the same set of probes?It seems like the time skew would be related more to the circuitry and cable length than anything else. Though temperature probably plays a role, I’d guess it’s less of a variable than other physical attributes.

author: tautech
author_rank: Super Contributor
timestamp: June 08, 2024, 12:48:23 am
content: Quote from: TomKatt on June 08, 2024, 12:26:49 amChannel Skew adjustment is not required when identical probes are in use.However particularly for the Power Analysis option, in order to get accurate computational results when Current and/or Differential probes are used their signal propagation delays need be nulled/aligned with the voltage probes, or vice versa.Siglent's Deskew accessory is just a handy method of providing a current loop for deskewing current probes and a voltage pick up point to connect voltage probes to.Deskewing Differential probes and current probes is much simpler and just a fast edge is required.

author: tautech
author_rank: Super Contributor
timestamp: June 08, 2024, 12:56:49 am
content: In this post probe propagation delays are quite evident vs the 10 MHz Leo Bodnar pulser waveform used as reference while testing probes.Pulser is BNC connected directly to the scope therefore the probe waveform from the same source shows very evident propagation delays.https://www.eevblog.com/forum/testgear/probe-into-probes-whats-up/msg4678768/#msg4678768

author: TomKatt
author_rank: Frequent Contributor
timestamp: June 08, 2024, 12:57:50 am
content: I was thinking about the power analysis feature specifically. If I use a deskew fixture to measure the timing of my current probe, is that time constant for that probe?Just wondering if I knew someone who had a fixture if I could measure my probe for future use. Unfortunately this person is not close by so I wouldn’t have ready access for every time I’d want to use the power analysis option.

author: tautech
author_rank: Super Contributor
timestamp: June 08, 2024, 01:06:41 am
content: Typically PA use will be for SMPS testing/qualification and working in the 10's of kHz.Siglent's Deskew accessory is operating ~20kHz which is near enough for many SMPS.If you have a Risetime spec for your current probe vs voltage probe you could make best guess skew adjustments/corrections.Or you could have a study here:https://www.eevblog.com/forum/testgear/scope-probe-deskew-fixture-pcb-project/

author: TomKatt
author_rank: Frequent Contributor
timestamp: June 08, 2024, 01:19:52 am
content: Thanks!I searched the forums for deskew but somehow didn’t see that thread. Pretty much exactly what I was looking for.

author: bdunham7
author_rank: Super Contributor
timestamp: June 08, 2024, 01:48:07 am
content: Quote from: TomKatt on June 08, 2024, 12:57:50 amIt's a matter of degree, but at typical PSU frequencies--say 20 to 250kHz--and probes of appropriate bandwidth, therelativeskew correction between two particular probes shouldn't change much with a little handling or temperature change. I probably would check a few times just to see what kind of variation you do see.