RF Current Probes Episode 1 - Basics

[@jluke6861]

Great Video. Thank you.

[@subramanianr7206]

A great initiative on the subject of the current probe, which is also the basis of understanding an SWR/power measurement in amateur radio. Keep producing more videos. Thanks. De VU2RZA

[@MachOneDesignEMC]

Many thanks for your feedback and we will try our best.

[@Torito1774]

Thank you, interesting video. Can we use a TBPCP1-20100 probe to visualise EMI in the frequency domain on a spectrum analizer or does it only work for time domain on an osciloscope?

[@MachOneDesignEMC]

Yes, absolutely. But most spectrum analysers start working from 9kHz, so you better check if yours is the same. I used Tekbox receiver which works from 0.1Hz. You should have no problem connecting it to an oscilloscope.

[@Torito1774]

@@MachOneDesignEMC Thamk you Mr. Zhang. They used to sell the Spectran NF-5030 at Aaronia but it has been discontinud for some reason. Maybe I can find a second hand one

[@tomasbergh]

Thank you for your videos, I like them a lot. But I wouldn't like to use a Clamp on ferrite like you do. If I am not wrong, the ferrite itself will attenuate the noise....

[@MachOneDesignEMC]

Hi Tomas, hope you have now seen Episode 2 and 3, when constructed properly and terminated properly, the attenuation impact is actually quite insignificant.

[@tomasbergh]

@@MachOneDesignEMC If you want to observe the current in a conductor by the use of a B-field probe and then adds a ferrite/inductor on the wire you want to observe the characteristics of the ferrite must affect the current! I feel confused if it doesnt! Of course I understand that you will get better coupling to the probe pickup. I will have to look on your video clips again I think. Thanks/Tomas

[@MachOneDesignEMC]

Hi Tomas, you do ask hard questions! I did a little bit of research on this subject, guess what? The answer is very complicated, maybe I will do a special episode on this. But to summarise, it is not as simple as we thought that a ferrite core will attenuate signals. Think about it, when a probe is clamped on a wire, it also increases the inductance of the wire of the EUT, isn't it? Because effectively, now you have a wire through a core, so it is now a better inductor to some extent. So it is not a surprise, that the added series impedance to the circuit under test depends on many factors, the main ones being mutual coupling, self inductance of the current probe, self inductance of the wire under test and the coupling factor between the two. Very complicated stuff. Eventually, if a probe is terminated with 50 ohm, that 50 ohm impedance will be reflected back to the wire under test and thus reduce the effect of series added impedance. Hence, we should never leave an unconnected/unterminated current probe on the wire under test.

[@tomasbergh]

@@MachOneDesignEMC Yes, exactly my point! Everything gets complicated when looking into details! 🤣 Sorry if bothering you! /Tomas