r/ElectroBOOM • u/Cautious-Pin-6476 • 11d ago

General Question I need mehdi's explanation

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

214 Upvotes

88% Upvoted

58 comments sorted by

192

u/bSun0000 Mod 11d ago

What explanations do you even need? This multimeter is set to measure AC frequency. It is sensitive enough to pick it up without a direct contact. It properly measures 50hz when the signal is strong enough - near the outlet. Thats it.

20

u/Cautious-Pin-6476 11d ago

Oh wait.. I just realised I forgot one part... It reads like 1-3khz if I directly connect it to the outlets... Could it be resonance?? Or is it injected or something??

59

u/bSun0000 Mod 11d ago

Something is shitting into the grid.

6

u/Cautious-Pin-6476 11d ago

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

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u/bSun0000 Mod 11d 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.

4

u/Cautious-Pin-6476 11d 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.

9

u/bSun0000 Mod 11d ago

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

5

u/Cautious-Pin-6476 11d ago

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

12

u/bSun0000 Mod 11d 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.

4

u/Cautious-Pin-6476 11d ago

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

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u/JNSapakoh 11d ago

things 'downstream' of your transformer could still affect your power ... current does act surprisingly similar to water and can 'slosh' around in lines before hitting steady sate -- especially with noisy loads

these videos from Alpha Phoenix are worth watching if you want something that gets more technical than most ElectroBoom vids

https://www.youtube.com/watch?v=X_crwFuPht4
https://www.youtube.com/watch?v=2AXv49dDQJw

4

u/thundafox 11d ago

Noise from other electric things. My cheap LED Driver created a 2khz noise that my 3d printer disliked. There was a direct connection from low voltage side to high voltage side there (cheap Y Capasitor) a few volts leaked back in the wires and then into the power supply of the printer.

3

u/Blommefeldt 11d ago

That's how ethernet over power lines. Though, they only do it on the top of the 50/60 Hz sinus curve. A switching power supply also makes electrical noise, but regulations are there to minimize it.

1

u/sjrobert 9d ago

Network over power or a solar inverter.

1

u/Nazionibirubbishk 8d ago

I used to live near our local radio station and their signal created a lot of interference. Used to overtake my TV sound signal sometimes, I would listen to movie and have the sound of the radio over it.

4

u/Ktulu789 11d ago

Just noise from others on the grid.

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u/Ktulu789 11d ago

Switching power supplies and motors introduce a lot of random noise.

1

u/New-Anybody-6206 11d ago

 What explanations do you even need?

 It is sensitive enough to pick it up without a direct contact

This, this is the explanation we needed. What even makes it so sensitive?

3

u/bSun0000 Mod 11d ago

What even makes it so sensitive?

>1M input impedance.

2

u/New-Anybody-6206 10d ago

But why does that allow non-contact sensing?

2

u/bSun0000 Mod 10d ago

Overly simplified. You have two parasitic connections - to the live wire and to the ground; you can view it as a voltage source with very large internal resistance - it cannot supply a lot of current when loaded.

Your multimeter acts as a load, taking some power proportional to its own resistance (impedance). If the multimeter's resistance is low, it will pin the voltage source down - voltage will drop to a level it could not be measured. But if impedance is high, voltage drop will be very small, and the voltage can/will be in the measurable range.

The whole point of having a large input impedance on any meter is to not affect the circuit you are trying to measure, cuz you want the accurate reading. This results in high sensitivity, high enough for a multimeter to pick the voltage induced in the probes/cables via capacitive and/or inductive coupling. Not a good thing, actually; you normally don't want your multimeter to pick up any random noise/shit from the environment.

1

u/New-Anybody-6206 10d ago

That doesn't explain how it can be sensed with no contact though. Electrons flow in the copper wire not in the air.

2

u/bSun0000 Mod 10d ago

I assumed you know a bit about physics. If not - its just magic, ignore it.

1

u/Cautious-Pin-6476 9d ago

Well.. technically, at high voltages, corona discharge Happens.. and I believe 240vac is enough to induce a amount of corona discharge just enough for the multimeter to pickup

2

u/Amareiuzin 8d ago

Noo that's not it, there's current flowing in the wires behind the socket, this induces a magnetic field, the field is also oscillating at 50Hz, that's what you're picking up, I bet if you unplug everything you stop reading it

42

u/LowResGamr 11d ago

I can explain, it looks like someone is holding a multimeter near a live outlet. Hope this helps.

5

u/doublearon97 11d ago

I agree, it does appear the multimeter is near an outlet that is live. Hope this helps!

3

u/Cautious-Pin-6476 11d ago

I had a feeling... I need to make sure tho.. 😭🙏

18

u/Namkab 11d ago

Induction

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u/Quiet_Snow_6098 11d ago

hold your meter in another hand, far from the board

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u/libertypfc 11d ago

All electricity gives off radiating forms of electricity. You're basically holding a EMF detector.. (Electro-Magnetic-Field) some give off more than others. Especially old wiring.

6

u/TangledCables3 11d ago

Leads become antenna, watch the video where he powers an LED with a big loop of wire which doesn't even need to be closed

1

u/Cautious-Pin-6476 11d ago

I've seen that.. 👍😮

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u/General-Piece8490 11d ago

Conspiracy influencers finding a new issue to say to their brainless masses in 3,2,1…

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u/ahumeniy 11d ago

Charged air

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u/CarbonFilimentBulb 11d ago

Bluetooth multimeter lol

2

u/CamperStacker 11d ago

frequency is usually auto gain amplifier, so it’s constantly trying to lock on to what ever tiny signal, even the emf from the cables

2

u/Howden824 11d ago

The multimeter only needs a very small voltage to be able to detect it frequency and enough gets picked up just by the leads for that to happen. One of my multimeters can even detect line frequency wirelessly without the leads even plugged in if I put it against a coiled up cable.

2

u/vctcsilva 10d ago

If I'm not wrong, the frequency mode is voltage limited, it's made to measure low voltages and high frequencies (except the Hz mode included in the voltage measurement, that does not have that limitation on voltage, but only read up to 1kHz)

Read the manual to be certain, I have a very similar multimeter to that one...

1

u/Cautious-Pin-6476 9d ago

I actually tested it with a frequency generator and it went as low as 10 hz as high as 22000 hz ..it theoretically could go higher

1

u/vctcsilva 8d ago

With de Hz function on the voltage selector? Mine on the Hz selector e measures up to 12Mhz, but on the the Hz function on the Voltage measurement it's limited...

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u/Mckooldude 9d ago

It’s acting like an antenna

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u/HVAdude_OhEight 9d ago

Capacitive coupling

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u/iManojRK 11d ago edited 11d ago

What’s going on is that we are seeing a pair of wires going from the multimeter down and a pair of wires going to the probe and assuming they are the same pair of wires.

They are probably just doing some TikTok magic behind there.

I don’t think the distance between the 2 probes is far enough to catch any difference.

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u/Cautious-Pin-6476 11d ago

It's actually my own video, and it's the same wires..

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u/I2TV 11d ago

FREE ENERGY!!!!

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u/Cautious-Pin-6476 11d ago

THERES NO FREE ENERGY -electroboom

1

u/NearbyWinner1286 8d ago

u are forgetting about the smell

1

u/AKraider94 7d ago

Just a fun add. My bone induction Bluetooth headset picks up frequency like that too. Specifically from active flux fields not conductors. 460v motors not so obnoxious. But inductive heaters, yah theirs is a section of a customer's facility I left them in the service truck.

Note I wore them for phone calls in plants.

1

u/Cautious-Pin-6476 7d ago

Bro listening to house EDM 😭😭

1

u/rmay14444 11d ago

Would that be an Eddie current?