EMF Neutralisierer, real or tinfoil hat?

[FriedMule]

I was looking for some way to shield the SMPS I have to power some of my electronic in my mini lab, and then I stumbled upon EMF Neutralisierers. It was on a site about the government spying, you know the usual stuff with aliens. But do the EMF Neutralisierers work and if, then how.
Could it be used in my lab to kill all the noisy signals from whatever?

[perieanuo]

Yup. Unplug everything especially your internet connection.nit kiddn


Envoyé de mon iPad en utilisant Tapatalk

[FriedMule]

So that means that it kills everything, mobile connection, wireless internet yes everything?

[mikerj]

I was looking for some way to shield the SMPS I have to power some of my electronic in my mini lab, and then I stumbled upon EMF Neutralisierers. It was on a site about the government spying, you know the usual stuff with aliens. But do the EMF Neutralisierers work and if, then how.
Could it be used in my lab to kill all the noisy signals from whatever?

The highlighted part tells you everything you need to know.   They do not work, they are just scams to relieve the paranoid of their money.

[FriedMule]

Thanks, great way to answer, so if I'm not afraid of the reptiles with laser guns and there body snatching, I shuld look at other sollutions. :-)
But then, how do I shield my power supply's so they do not "shout" all over my workbench?

[Ian.M]

Build a Faraday cage for them with all seams soldered or with conductive gaskets, and with filters bonded to the cage on all wiring in and out where they pass through the cage wall.   Alternatively get old-skool linear supplies with analog meters for when you need to work on EMI sensitive stuff.

[FriedMule]

Ian.M thanks, could you please show and tell more, how do I get more, real, info? I have searched but again, I stumble upon "my neighbor is an NSA-spy, an UFO was in my backyard and so on:-)

[radiolistener]

Switching power supply is a source of a strong RF noise. There is no way to eliminate that noise at all.
All what you can do is just reduce that noise at some acceptable level.
You can do it, by place switching power supply into metal box with no holes, use good RF-choke filters on the mains and DC output wires. Also, schematic and PCB of switching power supply should be designed to minimize noise leaks. It should use good quality inductors and capacitors and other solutions. Any long wire or hole in the metal box may leads to noise leak.

Any EMF shield and RF-choke filter just reduce noise leak, but don't eliminate it at all.

If your equipment is sensitive to noise and you're need low noise environment, then you will need very complicated, complex and very expensive EMF shield and filter solution. If your requirement is to get ultra low noise environment, EMF shielding for switching power supply will be almost impossible.

That's why linear power supply is better solution for low noise applications. Since it doesn't produce noise, it is more easy to protect your equipment from noise. But the mains is still source of noise from other electrical equipment. So, you're need to use good RF choke filters for mains.

For extreme low noise environment, it is better to get away from any mains and any electrical equipment and use battery for power supply.

[radiolistener]

Ian.M thanks, could you please show and tell more, how do I get more, real, info?

you can google it. Here is some basic info for example:
- https://www.ato.com/how-to-reduce-switching-power-supply-noise
- https://vtechworks.lib.vt.edu/bitstream/handle/10919/83372/Yang_Y_D_2018.pdf?sequence=1

Actually, if you're need low noise power supply, this is not so easy task.
And requires very strong electrical and physics knowledge.
It will be more easy and cheaper to use linear power supply for noise sensitive equipment.

[FriedMule]

As a noob my concern is not so much precision or technical gear's behavior but more me as a noob making mistakes, measuring wrong or fighting with strange results, because a SMPS is laughing at me, under my desk.
I have i.e. two UNI-T products with SMPS and also some LED lights that also make a lot of noise, so my hope was to shield most of it from my measuring, either by building some sort of closed box, shielded cables or by suing the aliens. :-)

My hope is to reduce my chance for using hours, chasing an "error" that is all coursed by some electronic noise.

[coppercone2]

look at military EMI filters for TEMPEST grade $$$

[Brumby]

Another Idea is to set up your workbench so that you can "rig for silent running".  By this I mean you identify every bit of RF noisy gear and be able to remove power from them when you need a low noise environment.  It might be worth trying out Dave's $10 EMC probe idea to see what's noisy.

Desktop computers would need to be unplugged as even when they are "off", there is power flowing so that the soft on power button can work.  If you want to be critical, view tablets with suspicion and take the batteries out of any laptops and phones.

Electric motors in vacuum cleaners, fans and kitchen appliances (just to name a few) can be really ugly if they are on the same circuit as your lab, but even if they're not, just being nearby could be enough to ruin your day.  And if you've got someone doing arc welding in the area - go do something else until they're finished.

For lighting, use an incandescent globe or LEDs powered by a linear constant current source from a battery or simple old school transformer power supply.  LEDs and steady DC are a brilliant combination.

If you need to run a scope which has a switching supply, then I suggest you try an Dave's EMC probe to find out just how much hash it is introducing into the environment - and what it looks like - so that you can take that into consideration.


There's a lot more that can be said - but you get the idea.

[FriedMule]

Thanks for the great tips.
Yes it is about to kill all noise sources but some is properly hard to be without.
When Dave do tear down of more expensive gear, there are often some sort of metal shielding, to shield against RF and EMF, would it not be possible to make a box and place the SMPS inside that box?

[dmills]

The trick with screening boxes is that any slits or openings must be thought about carefully (they form radiators at a high enough frequency), and every electrical connection penetrating that box must be filtered in a way appropriate to the problem you are trying to solve.

Also the metal must be thick enough and of sufficient conductivity to make the skin depth at whatever frequency you care about much less then the thickness, this is HARD at low frequency.

Bringing all the wiring out from the same side of the box is a good idea, as is keeping the internal doings only connected to the box at that edge (reduces circulating currents in the box walls).

Really switchers are fine, even for low noise work, you just have to do the sums to see what you need to do to make the power supply noise a non issue, and then follow thru.

Now filtering the output across a sufficiently broad band, that can be tricky, a post switcher LDO helps, but usually the PSRR goes to pot surprisingly quickly (But they will deal with most of the annoying DC - 1MHz or so region), then LCR filters for the quick stuff.   

Regards, Dan.

[radiolistener]

all depends on what is your requirement for low noise.
If you're need to work with signal levels about -40..-50 dBm, then switching power supply can be shielded with no problem.
If you're need to work with -80..-110 dBm, then shielding may be complicated or even problematic.
For signal levels -130..-150 dBm even good quality and good shielded switching power supply will be a problem.

[FriedMule]

I do not know the frequencies or db I want to avoid but maybe you can try to help me find out?
I think that I want to work with low frequencies, under 3GHz but mostly under 1GHz.
It is Audio, logic circuit, SMPS, Bluetooth and that kind.

[radiolistener]

If you're planning to use it for sensitive RF receivers or high quality audio, then switching power supply is a bad choice.
For oscilloscope measurement it is ok, but you're need good shielding.
For logic circuits it almost doesn't matter.

[coppercone2]

it will reduce noise margin and cause jitter

[coppercone2]

Thanks for the great tips.
Yes it is about to kill all noise sources but some is properly hard to be without.
When Dave do tear down of more expensive gear, there are often some sort of metal shielding, to shield against RF and EMF, would it not be possible to make a box and place the SMPS inside that box?

your not radiating all the noise. the line has some impedance at high frequencies still (its not a open circuit) so you can conduct some noise, or conduct some noise out the wire (its an antenna, may be very inefficient), radiate it, and absorb it some other way. Or just directly conduct it.

you need shield and filter.

the filter works this way: your supply has some output impedance, your load has some input impedance. you want a filter between that. those impedances are not constant so passive filters are not going to work that well or be obvious how to implement in a correct way. Better not to make the noise. It's difficult to make a filter for changing impedance (based on load).



since the shield is not perfectly 0 impedance, and it does not shield fully, it is possible to make the situation worse.


and look out for negative resistance behavior if you are filtering a DC rail to a another switching converter.

Look at the documentation for EMI DC rail filters to get you an idea of how it works.

[FriedMule]

I know that it's all about what the target result is. Since my gear is not honorable member at NASA and I am not trying to shield medical equipment. My goal is just to remove as much noise as possible, without being insane. :-)
The leads may radiate noise also and there may also be noise trough the outlet but if I just want to "turn it down" so I do not get fooled to much while playing with hobby electronic.
A person as Dave do not need to shield or if he do, we are talking about something wary serious because he does not get fooled by what he sees on the scope or if the Dmm is behaving strange. But my lack of knowledge does that I get wary easily fooled and just want to avoid that. :-)

My hope was a not to fare out solution where i.e. I could put all the noisy stuff into a metal box, close the box and thereby reduce the noise to something less then if without any shielding.

[radiolistener]

My goal is just to remove as much noise as possible, without being insane. :-)

The best way to remove noise is to not produce it. 
If you're worrying about noise, then just use linear power supply. It doesn't produces RF noise at all.

If noise doesn't matter for you and you want to get better efficiency and lightweight power supply, then switching power supply is your choice.

For example, if you're need power supply for home heater, electric stove or powerful electric motor, then switching power supply will be better than linear one.

But if you're working with analog electronics, amplifiers, VCO, DAC, ADC and other analog stuff, then linear power supply is better.

[FriedMule]

Yes all what I make my self, could easily be with linear psu, but some of my lab gear has smps in the plug side on the cord, my shop light is LED and fluorescent lamps. I hope to build smps myself so it would be nice if the other did not make noise to.

So I do not have the easy choice to "just don't use smps", therefore my hope on reducing there noise without going overboard.

[radiolistener]

try to put RF choke ferrites on all wires. As many as you have, on any wire in your lab, like paranoic. It can help for a little 

[FriedMule]

great idea, and how do I shield the smps to chaise noise?
Dave talks in a video about a cast alu box for shielding, would that contain the smps-noise inside the box?