EMC debugging - Near field Magnetic field probes
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- Опубликовано: 1 июн 2024
- #81 In this video I continue looking at near field probing methods by analyzing Magnetic field probes. I start off by generating magnetic fields using a Helmholtz Coil and them I proceed to measure it using a selection of magnetic field probes. I analyze the main noise related issues and afterwards I proceed to look at a practical circuit, both with the magnetic field probe as well as the electric field probe.
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Usefull links: en.wikipedia.org/wiki/Helmhol...
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11:19 - By observing this waveform of emission I clearly see that it's a flyback converter. Thank You a lot for Your great job!
The best practical explanation, you are an excellent teacher.
Again, I know about this generally but this is now very clear -- many thanks.
Excellent video! Thank-you so much for the clear, logical explanations. I have a set of commercial near field probes with a wideband amplifier and your content has already helped me to use them more effectively.
Great. Very nice improvment in the video recording and lighting. I enjoyed the video. ..
Thank you! I went from a single front facing light, and the one on the ceiling to about 3 lights all at roughly eye level. I turned to LED lights since these are more efficient, and I had to add some kapton tape to them to turn the color a bit more yellow, but it seemed to work out quite well.
when i see it's your channel, the protocol is to give a thumb up first, then watch
Very educational video. Many thanks for your efforts to spread and share your knowledge.
Great video. A lot of useful, practical information helping understand how to use the near field probes - even though it's almost 15 minutes long I enjoyed every second of it. Great job
What an interesting topic. I didn’t even know this was a thing. Thanks!
Really great.
Thanks
Thanks from turkey
Great video. Thank you for connecting theoretical dots with the practical in a simplified way. I use Langer EMV test probes but now I know these DIY probes too.
The sound and video quality improved a lot. Keep on doing good videos.
I also tried out some probes from Langer, great professional tools and quite a wide variety! The DIY probes are more useful though in DIY situations when there is no point in investing in expensive equipment; but both work on the same operating principles.
I'm happy you are enjoying the videos!
The unfortunate reality of failing an emission test is not just the costs, but in determining how is the energy is being radiated (where is the source and its associated antenna). Meaning, the design could be electrically sound, but there is a shortcoming due to PCB trace design, PCB stack-up or perhaps both. So, before going into the EMC lab you would do what is called EMC pre-qualification. The most basic tests are done near field for E and H fields. But, depending on the size or your product you can actually have a small far field anechoic chamber, which is not as good as the lab, but good enough for pre-qualification tests. Once pre-qualification is done you can then now pass your tests at the EMC lab.
There is a corollary in EMC design. In that a design which confines EMI in reduction of emissions is also usually very effective in reduction of susceptibility.
Really nicely done sir. As a SMPS engineer, seeing those flyback waveforms really makes my feel at home. Never thought I could learn so much from a non power electronics dedicated channel.
Also that your mentioning about impedance matching is brilliant, no textbook clichés but for the first time I really grasp what it is about.
And one more question: should I make the electric shield of the magnetic probe with copper and ground it for optimal performance?
Grounding the shield will help to reduce the pick-up of electric fields, so its quite useful. In my probe I used aluminum since that is what I had available, but copper is better since it can be soldered.
Let me know how it turns out!
Thanks FesZ, great video
I'm happy you enjoyed it!
Спасибо, интересное видео!
Awesome
Very interesting Video Thank you
I'm happy you enjoyed it!
Amezing video. Create a video on DIY probe with calculation.
I enjoyed the video thanks
Thank you for video. Can you recommend me a type (or may be a model) of magnetic field probes, which can measure field lower then 1 microT (50 - 1000 nT)?
can you use to oscilloscope probes to test the antenna probes by interfacing it with the oscilloscope?
Very nice video. I would love to see you try these home-made probes on commercially available power supplies, that you know have passed the EMC tests. That might give us another interesting and useful comparison. Cheers!
Just because a product passes EMC tests, doesn't mean it has no emissions. A near field probe is not useful to verify compliance, but rather to identify noise sources. It will tell you what part of a circuit is noisy, but it will not tell you if that noise is enough to cause a compliance issue.
@@FesZElectronics Got it. Thanks!
Thanks so much for the video and explanations. I also want to share this:
In the 1990’s I worked in an AV shop as a service tech and my boss at the time who owned the service center was an electronic genius. He could look at any schematic at all and within seconds describe in detail what it was and how it worked. He told me he was working on inventing a probe that would read the signals off of ic pins on the scope without physical contact. He did not give any details for obvious reasons. I since quit that job and he moved back to Greece but I wonder if his concept spawned off the near field probes.
I'm not sure when the first probes for PCB circuit debugging where made, but the "near field" measurement technique was initially used to measure antennas (see how well they transmit) starting in the 1950s. But I guess that before the EMI compliance requirements where not that strict this sort of probe was not necessary so its invention could be quite recent.
Hi FesZ ; When you connect the 50 ohm termination does the signal amplitude get diminished ? After all 50Ohms is a pretty big load . Love your videos, they are fantastic !
The temination will reduce the signal to some extent, but it will reduce the noise even more - so it improves signal-to-noise ratio. Anyway, magnetic fields generate a current rather than a voltage (as is the case with electric fields), so a well defined load needs to be provided.
How are the probes for detecting brainwaves made ?
Hey how can I measure magnetic field of high frequency with Beehive Electronics 100B EMC Probe?
excellent comparison, an idea came to my mind when i see how directional it is and the phase invention of the magnetic probe: Can you make an omnidirectional magnetic probe by combining three coils orthogonal to each other?. then i remember my physics class about Maxell equation where divergence of B is always zero, but in my proposition there is not a close surface were calculate this divergence. I think will be an interesting experiment to try.
Actually, "3D" coils are used in NFC (near field communication) devices working on the 125KHz band. Its commercially available as a single component with 3 coils on the 3 axes and the point being to be sensitive in any direction to the low frequency magnetic field.
is it always recommended to hold the H-field probe parallel to the PCB trace for obtaining stronger magnetic field ?
Not necessarily. Depends on what exactly you are trying to measure. The orientation that gives the strongest result will help you determine the exact source of the noise.
Can we connect a magnetic probe to an FPGA board?
hi does the loop size affect the sensitivity to different frequency?
Size should not affect frequency response. Most commercial probes will work up 3-4GHz. I guess the biggest issue is maintaining constant parameters over the entire frequency range - the cables and dielectric need to have low losses and controlled impedances up to the desired frequency.
@@FesZElectronics thanks!
@@FesZElectronics btw, how bout i increase the loop counts? what effect will i observe?
Hi yer fez a question for you about mains cable take oley flex 110 CY copper shielded cable if you to remove the clear but separate with heat shrink and Aluminium braid the separate and add stainless steel braid then add a final braid of Mu metal would this be an ideal earthing shielding arrangement for 220/240 volt 50/60 HZ cable and combing the the earths at plug end could you do a vid on mains cable for hifi and hope you have a good one 👍👍
can you explain a little bit in detail as to why you need a tiny gap on the outer shield....?
If the shield is continuous, it forms a single turn inductor which is short-circuited (since the turn is continuous) - so any magnetic field will induce a current into this rather than the probe and you will not be able to measure anything.
Ok understood… but how will the currents be induced by the magnetic field in the inner conductor( inner wound/looped wire in your demo) when you have shield/metal over it? How is that the magnetic field is able to penetrate this shield and induced currents in the Inner conductor?
Btw you make amazing and very clear videos. Keep the good job up…
Thanks