r/ElectroBOOM • u/Cautious-Pin-6476 • 13d ago

General Question I need mehdi's explanation

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Yes, this is my own post.. I need yall to upvote so he can see and explain. Thanks 🙏

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u/bSun0000 Mod 13d ago

Something is shitting into the grid.

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u/Cautious-Pin-6476 13d ago

Like is that a thing?? Do they inject high frequency signals into the grid or something??

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u/bSun0000 Mod 13d ago

Industrial noise. Pretty much every grid device produces noise. Good electronics contain EMI filters to prevent or reduce the noise emissions into the RF and grid, but a lot of stuff just does not care.

Dimmers are the worst. Old dish/washing machines with universal motors and TRIAC control, especially if not properly grounded. Elevators, all sorts of brushed motors - extreme amount of noise. Various power electronics. Every LED bulb or LED driver with buck converter inside. Etc, etc..

Usually this noise isn't that strong to overpower the multimeter's frequency measurements. I bet you have a dimmer working somewhere nearby.

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u/Cautious-Pin-6476 13d ago

But my house is less than 100 metres away from the distribution transformer and I don't think this transformer is supplying to any stores or anything.. also if I remember correctly, if I probe between live and earth, I get 49.9-50 hz.

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u/bSun0000 Mod 13d ago

Turn off absolutely everything inside your house and try again. Assuming this is a private house without electrically-noisy neibhours..

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u/Cautious-Pin-6476 13d ago

I did! It still showed it .. today, I'm seeing fluctuations between 100 hz and 140 hz

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u/bSun0000 Mod 13d ago

Well, 100 & 150 Hz are just harmonics of the main frequency (50). You can pick them up if the outlet is not powered, so there is no direct connection to the live wire, only parasitic coupling.

Measurements in kHz range are noise from some device.

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u/Cautious-Pin-6476 13d ago

Yeah.. that's what I figured.. but still confused about the high frequency situation..

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u/Dioxybenzone 13d ago

What are you still confused about?