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| Oscilloscope probe ground leads act as FM attennea |
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| ebastler:
--- Quote from: Fungus on October 29, 2023, 10:59:19 pm ---Nope. The GND is connected the BNCs internally so no chance of a loop. ;) --- End quote --- Well, there is a GND connection between BNC and Ref GND clip inside the scope, and one outside the scope (if you make the cable connection). That's a GND loop, right? But when you say "Nope", you mean you tried and it changes nothing? Then that loop is not where the scope picks up noise -- or you live in an electrically quiet area. |
| Fungus:
--- Quote from: ebastler on October 29, 2023, 11:08:12 pm ---But when you say "Nope", you mean you tried and it changes nothing? --- End quote --- Yep. It all looks great either way. --- Quote from: ebastler on October 29, 2023, 11:08:12 pm ---or you live in an electrically quiet area. --- End quote --- Looks that way. |
| dmulligan:
--- Quote from: CosteC on October 28, 2023, 05:48:38 pm --- --- Quote from: iMo on October 27, 2023, 12:21:47 pm --- --- Quote from: CosteC on October 27, 2023, 11:43:42 am ---.. What is possible far easier in DHO800/900 is to add ferrite core on PE/grounding lead which may help in some cases. --- End quote --- That will not help you in any cases, imho. The ferrite bead put on a grounding wire will introduce serial impedance, like 10-100 ohm based on frequency.. You want the opposite - to have as small as possible impedance towards the ground.. --- End quote --- In general you are right, yet in this case environment seems very noisy, maybe PE is noisy too. Putting ferrite on cable is easy experiment. Probably it shall be on emitting device, yet it may be celling light, so somewhat difficult. --- End quote --- I found a snap on ferrite bead on an unused cable. 27mm long and 9mm ID (has a plastic cable holder). I tried looping the ground cable and the USB-C cable or straight through with the AC cable with no noticeable difference. I even tried the probe ground lead for fun which made a significant difference for the worse. Oh well. I know how to work around the noise by using the ground spring which is good enough for now. I still hope to find out how to avoid it all together. Maybe I'll have to move in with Fungus since he lives in a exceptionally EMI quiet area. |
| CosteC:
Ferrite on ground lead - as expected :) Any luck with turning OFF some stuff in room/home? LED lighting can be very noisy and LED strips are naturally long, good antennas. Another classical issue source are variable frequency drives. Now in washing machines, fridges, air conditioners and other stuff with electric motors. EV cars are also horrible. I would be surprised if EV chargers would be different. Many kW SMPS always emits. |
| dmulligan:
--- Quote from: CosteC on October 30, 2023, 05:54:32 pm ---Ferrite on ground lead - as expected :) Any luck with turning OFF some stuff in room/home? LED lighting can be very noisy and LED strips are naturally long, good antennas. Another classical issue source are variable frequency drives. Now in washing machines, fridges, air conditioners and other stuff with electric motors. EV cars are also horrible. I would be surprised if EV chargers would be different. Many kW SMPS always emits. --- End quote --- A few days ago I reported that I turned everything off and unplugged all the things in this room with no significant change. I am waiting for an opportunity to shut off all breakers in the house and turn them back on one at a time. There are so many devices in my home, it could be coming from anywhere. Is this why people wear tinfoil hats? |
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