B EMF Radiation detected from TV

[ChrisCOD]

Hello. I have a quick question in regards to EMF radiation. In particular, I would like to know what quantity of microteslas a smart TV would emit. In particular, would it be unusual for a smart TV to emit in excess of 1000 microteslas even when turned off? Thanks.

 

[Drakkith]

Microteslas are a unit of measurement for magnetic field strength, which isn't something 'emitted' in the usual use of the word. For EM radiation we typically use units of power or energy, like Watts or Joules. In terms of power emitted as non-infrared EM radiation, the amount emitted when a TV is turned off is going to be substantially less than the power draw the TV has when turned off (since most TV's are in 'standby' mode, not actually turned off). If the standby power draw is, say, 5 Watts, then almost all of that power is lost as heat transfer to the air or as IR radiation. A very tiny amount is turned directly into EM radiation through non-heat related radiative effects.

 

[ChrisCOD]

Microteslas are a unit of measurement for magnetic field strength, which isn't something 'emitted' in the usual use of the word. For EM radiation we typically use units of power or energy, like Watts or Joules. In terms of power emitted as non-infrared EM radiation, the amount emitted when a TV is turned off is going to be substantially less than the power draw the TV has when turned off (since most TV's are in 'standby' mode, not actually turned off). If the standby power draw is, say, 5 Watts, then almost all of that power is lost as heat transfer to the air or as IR radiation. A very tiny amount is turned directly into EM radiation through non-heat related radiative effects.

Ok. So in terms of microteslas, would it be normal to measure in excess of 1500 from a smart TV that is turned off? If so, what would be inside the TV that would cause this observed measurement to manifest?

 

[Drakkith]

I'm not sure. My phone's magnetic field detector app shows an ambient field of about 10 microtesla, which goes to 50 when I lay it on my metal desk, and actually decreases to around 5-6 microtesla when placed near my monitors or my smart tv.

 

[f95toli]

It could simply be that some part of the TV chassi is magnetic. The earth's background field is about 50 microTesla (depending on where you are). if you were to measure the field next to a regular refrigerator magnet you would measure a field of many thousands of microtesla (=many milliTesla). The field next to a strong rare-earth magnet would be millions of microTesla (=Tesla) .
One wouldn't usually use "tesla" to mesure EMF, it is usually measurement of static magnetic fields.

 

[Vanadium 50]

As said before, Teslas have pretty much nothing to do with radiation.

10,000 uT is about the field strength of a refrigerator magnet.

A loudspeaker, which your TV likely has, would probably be more.

 

[sophiecentaur]

A loudspeaker, which your TV likely has, would probably be more.

You beat me to it.
In the days of large shadow mask tubes, I'd bet you could measure the local 16kHz non-radiating field with an analogue multimeter and small coil of wire.

 

[Klystron]

Hello. I have a quick question in regards to EMF radiation.

Generally, EMF refers to low frequency electromagnetic fields such as those surrounding an active AC wire. Most communication devices such as your smart television and telephone receive and transmit radiofrequency (RF) radiation that can be detected with a variety of handheld devices.

Most RF detectors consist of an antenna connected to circuitry that allows humans to see a signal by deflecting a calibrated meter or watch a waveform, or to hear an audible whine or beep by modulating the RF into a frequency range suitable for human ears. The latter audible detectors are common inexpensive devices, often seen in high tech spy movies, used to isolate an RF source, usually indoors.

Many RF meters are calibrated using logarithmic or other scales for technical reasons, supplying readings in decibels or decibel-meters for audio signal outputs and power in Watts/meter² for power meter deflections.

A cursory online search for "RF detector" yielded this page of electronic devices as examples.

 

[ChrisCOD]

As said before, Teslas have pretty much nothing to do with radiation.

10,000 uT is about the field strength of a refrigerator magnet.

A loudspeaker, which your TV likely has, would probably be more.

If loudspeakers were responsible, would you expect uniform measurement either side of the smart TV? Would you be able to review my video on youtube which shows this and give me your view?

 

[Drakkith]

First and foremost, the "Detected High Radiations" warning is downright wrong. There is no radiation coming from that TV (other than regular IR due to its temperature). You are reading the magnetic field, not the emitted radiation. I think your app is trying to fool you into thinking that its beeping and warning message means it has detected something dangerous. It has not.

Also, what units was the 2nd app using?

Overall I didn't see anything worrying. Those magnetic field strengths, even if true for the 1000+ microTesla readings, are not a concern.

 

[f95toli]

If loudspeakers were responsible, would you expect uniform measurement either side of the smart TV? Would you be able to review my video on youtube which shows this and give me your view?

Sure, why not?
That app is most likely using the built in magnetometer in your phone, the same magnetometer that is normally used as a compass and assist in navigation. This means that it is reacting to the STATIC magnetic field from the TV, it is NOT what one would normally think of as radiation.
The field detected is only a few hundred microTesla which is not a large field, Again, a normal refrigerator magnet generates much larger fields.

 

[sophiecentaur]

Hello. I have a quick question in regards to EMF radiation. In particular, I would like to know what quantity of microteslas a smart TV would emit. In particular, would it be unusual for a smart TV to emit in excess of 1000 microteslas even when turned off? Thanks.

There is one important point that should be made here. The term "radiation" actually implies energy being launched out into space and being lost to the system. However, the levels of local energy can be a lot higher than the radiated energy. It all comes down to the phase angle between the E and the H fields. Locally, they are mostly in quadrature and the energy is reactive but, after a wavelength or so, the reactive energy is diminished and then radiated energy (in which the remaining vectors E and H are in phase) is all that's left. We then treat the structure as an 'aerial' and the radiated power depends more on the actual size of the structure. For a badly built mains transformer, the local leakage field can be very high and easy to measure but, after a few wavelengths ( many tens of km) the actual energy radiated is tiny. (I'm not referring to the inverse square factor here but the mode change of the field oscillations.)

 

[ChrisCOD]

As said before, Teslas have pretty much nothing to do with radiation.

10,000 uT is about the field strength of a refrigerator magnet.

A loudspeaker, which your TV likely has, would probably be more.

First and foremost, the "Detected High Radiations" warning is downright wrong. There is no radiation coming from that TV (other than regular IR due to its temperature). You are reading the magnetic field, not the emitted radiation. I think your app is trying to fool you into thinking that its beeping and warning message means it has detected something dangerous. It has not.

Also, what units was the 2nd app using?

Overall I didn't see anything worrying. Those magnetic field strengths, even if true for the 1000+ microTesla readings, are not a concern.

First and foremost, the "Detected High Radiations" warning is downright wrong. There is no radiation coming from that TV (other than regular IR due to its temperature). You are reading the magnetic field, not the emitted radiation. I think your app is trying to fool you into thinking that its beeping and warning message means it has detected something dangerous. It has not.

Also, what units was the 2nd app using?

Overall I didn't see anything worrying. Those magnetic field strengths, even if true for the 1000+ microTesla readings, are not a concern.

So the microtesla count is not a concern. But what would be inside the smart TV to cause that measurement? The only thing that I have come across is the internal speakers, because they apparently contain magnets. The only problem is that the microtesla count is non uniform on either side of the TV. This is repeatable, which is something I dont think you would expect if it was the speakers.

 

[f95toli]

So the microtesla count is not a concern. But what would be inside the smart TV to cause that measurement? The only thing that I have come across is the internal speakers, because they apparently contain magnets. The only problem is that the microtesla count is non uniform on either side of the TV. This is repeatable, which is something I dont think you would expect if it was the speakers.

There could be many reasons. The speakers are still a likely source since modern TV is likely to contain quite a few (since they often try to to create a simple form of "surround sound").
However, it could also be that part of the structure of the TV is made from iron that has become slightly magnetized.

For fun I just tried waving my phone around my desk and I am registering about 150 uT near the metal legs of my desk....

One thing worth keeping in mind that the sensors in your phone is meant to be used as a compass, this means that they are designed to measure fields that are at most around 50 uT or so and won't necessarily be calibrated (or even linear) for higher fields. Don't expect the results to be even remotely accurate if you try to measure much higher fields, they might end up showing nonsense values.

 

[davenn]

This is repeatable, which is something I dont think you would expect if it was the speakers.

of course it is repeatable..... the magnetic field of the permanent magnets in the speakers
of the TV do not change in strength