This video started slow with the basics, but ended up making some good points about common mode vs differential mode noise, and pcb track design. Thanks
Hi, nice video. I have a doubt.Why are there two push-button switches on the Demo Board? One is for connecting the GROUND and what is the other switch for?
Thanks. One connects the grounds at both side directly, the other connects the grounds through a capacitor which allows only some of the high frequency content to pass.
Definitely didn't come down as much as I expected it would, but for sure several of the harmonics came down by 10 or more dB. I think one issue is that the connections made by pressing the buttons were far from low impedance - the buttons were on the top side of the PCB, the leaded package inductance would be high and the tracks are very thin - all leading to higher inductance. Some current was still flowing around the ground plane slot. More investigation to be done here for future vids!
Very nice video. Subscribing. There is a confusion I have however. How is that the return current is exactly underneath the track (that is following the path of least inductance) at only 1kHz of the signal in 5:30. I though this effect happens only at higher frequencies which are above 100 kHz. Isn't 1kHz too low for the current to choose the path of least inductance? Thanks
It's a gradual effect as you can see from the simulation. As I mentioned in the vid, if the resolution were higher, I'm sure you'd see a tighter concentration below the wire at 100 kHz. The paper has more information on page 38 (www.jastech-emc.com/papers/IEEE-EMC_TP4_2009.pdf). Maybe I'll do a vid in the future with the EMSCAN unit and a sine wave input to see the effect.
