EMI Near Field Probing Basics - Page 1
Forum section: electronics / beginners

author: metrologist
author_rank: Super Contributor
timestamp: January 17, 2023, 02:58:42 pm
content: This video caused me to buy a twelve dollar EMI probe set, so I felt you tea partiers needed to be infected too...And of course, accolades to our host...

author: metrologist
author_rank: Super Contributor
timestamp: January 17, 2023, 03:00:06 pm
content: And if twelve buck is too steep for you...

author: mawyatt
author_rank: Super Contributor
timestamp: January 17, 2023, 06:28:42 pm
content: Can one get a $12 Probe Set that produces reasonable/repeatable results?Best,

author: pdenisowski
author_rank: Super Contributor
timestamp: January 17, 2023, 06:47:22 pm
content: I actually just finished a video on near field probes - it should be uploaded to the Rohde & Schwarz Test and Measurement Fundamentals Playlist in a couple of weeks:https://www.youtube.com/playlist?list=PLKxVoO5jUTlvsVtDcqrVn0ybqBVlLj2z8(I'm told it will also be turned into a web page on the R&S website, but no URL yet)I do have to say that I very much enjoyed Dave's videos on near field probes - really good stuff with a lot of solid practical advice.Quote from: mawyatt on January 17, 2023, 06:28:42 pmI tried out a bunch of probes while doing "research" for my video. The short answer, in my experience, is that there are differences in terms of things like sensitivity, frequency range, etc. between probe sets: a spur you can clearly see with a probe from one set might not be visible using a similarly-sized probe from another set.I spent many years doing field interference hunting and joked that there were some emitters that you could find with just a wire coat hanger and an AM radio- you needed the "good" antenna for the medium-hard and hard ones. The same thing applies to EMI debug - you can find the really egregious violations with more or less any probe, but the more difficult cases can often benefit from a better-quality probe. YMMV

author: metrologist
author_rank: Super Contributor
timestamp: January 18, 2023, 02:55:58 pm
content: I think they are like antennas. Maybe not so much the quality as other attributes of the design? I made a pretty good reflector bi-quad antenna as a feed for a 10-foot dish, out of basically coat hanger and fine chicken wire fence material. A littlewith a good VNA and voila! Who said 13 cm ATV could not go 25 miles los with a mere 50 mW? Maybe no oneBTW, I may get access to a professional NF probe set and try a comparison - something like this...https://www.testequipmentdepot.com/aaronia/accessories/probes/emc-near-field-probes-kit-pbs2-5-pa.htm...but with a ball detector so I may roll my own of that style.

author: pdenisowski
author_rank: Super Contributor
timestamp: January 18, 2023, 04:21:29 pm
content: Quote from: metrologist on January 18, 2023, 02:55:58 pmThat's pretty much what I didOne of the near field probe sets I used in my comparison was our (R&S) own HZ-15 set:https://www.rohde-schwarz.com/us/products/test-and-measurement/oscilloscope-probes/emc-near-field-probes-for-oscilloscopes_63493-73798.htmlThere was a (third-party) review of them in EDN many years ago:https://www.edn.com/review-rohde-schwarz-hz-15-near-field-probes/From my own experiments, there absolutely is a difference in performance between "professional" and "hobbyist" probes.If you do have a chance to do a comparison, you may want to consider preamplifier performance as well. In my investigations, the performance of preamps intended for use with near field probes varies significantly, especially with regard to noise figure.

author: metrologist
author_rank: Super Contributor
timestamp: February 09, 2023, 04:14:57 pm
content: I received my probes. Two of them did not detect any signal and perplex me. The SMA connector center pin is left floating. Is that proper? I don't see how they could work at all like thisLet thebegin

author: metrologist
author_rank: Super Contributor
timestamp: February 09, 2023, 07:36:02 pm
content: Here is another picture. How could this possibly work? I bet they just forgot to lay out the center trace and just decided to sell them anyway.

author: Momchilo
author_rank: Regular Contributor
timestamp: February 11, 2023, 04:37:47 pm
content: You can't remove the heat shrink tube. Now there is no longer a closed waveguide between the probe tip and the connector