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I am a medical researcher and I found an effect that I think I understand half way, but not completely and I hope someone more skilled in electrical engineering can clear this up for me. I am a novice on the field, so I aplogize in advance if it is a silly question.

I am working with two systems. System A produces an electromagnetic field that constantly and quickly changes it's polarity. System B produces strong electrical pulses (frequency unknown). I have noticed an effect, where activation of System B interferes with system A if (and only if) they are plugged in the same power outlet. I know from my hobby as a DJ that the power supply can be "bad" or "noisy", and that systems with LC-Circuits can cause this interference. I suspect this to be the case, but since I am pretty ignorant in the field I do not know how to verbalize the problem and where to start looking. I would like to know two things:

Is there a clear concept on how these circuits interfere with the power supply?

What can be done to avoid this problem? I foggily know that one should plug the systems into two different phases (dependent on two different fuses I think?) but this is all a bad case of half-knowledge.

Is there a piece of hardware that guarantees a "clean" power supply?

Thanks in advance. In clearing this up, you are helping me significantly.

Edit: System A is an electromagnetic field generator used for tracking purposes. System B is an electric scalpel. System A produces a high frequency field that constantly changes polarity and system B produces strong pulses electric pulses that it uses to cut tissue.

The interference is independent of physical proximity. I can disable the effect if I use two different outlets.

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  • \$\begingroup\$ You might get a better answer if you explained more about the types of equipment. Other than that it's a page or two of generalisations about Electromagnetic compatibility issues that will get boring to some. I could guess that your AC supply may not be as robust as it should be or even that there is air-borne interference due to them being physically close but nothing beats YOU telling us what the equipment is. \$\endgroup\$
    – Andy aka
    Commented Sep 27, 2013 at 11:10
  • \$\begingroup\$ I added the nature of the two systems. I'm sorry, I'm not intentionally being vague, both are proprietary and I do not know the inner workings. I am completely happy with a basic explanation or even pointers to literature - I literally don't know where to start on this. From what I gathered in the meanwhile it could be a "mains hum" effect. Can that be induced by other systems? \$\endgroup\$
    – Keno
    Commented Sep 27, 2013 at 13:15
  • \$\begingroup\$ OK what are the symptoms - lights flashing? Noises? dancing girls lol? \$\endgroup\$
    – Andy aka
    Commented Sep 27, 2013 at 13:28
  • \$\begingroup\$ Does he describing a device known as a line filter? \$\endgroup\$ Commented Sep 27, 2013 at 14:13
  • \$\begingroup\$ If only the bass dropped... =) The tracking device loses the ability to track, apparently because the field is malformed. I repeat, it is NOT proximity, although it sounds like this. I moved both devices into different rooms, and the effect only happens when both are plugged in the same outlet. proximity effects are there, but much smaller, I quantified them already. \$\endgroup\$
    – Keno
    Commented Sep 27, 2013 at 16:04

2 Answers 2

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Since the interference is noticed only when the equipment is plugged into the same outlet, I would suspect that System B is producing electrical noise that is being conducted out onto the power line. Switching power circuits can generate a tremendous amount of noise, and much effort is spent on reducing it to an acceptable level. In this case, it's hard to say whether system B is especially noisy, or A is sensitive to power line noise.

Typically, we try to address conducted noise problems by using some kind of line filter in the equipment, a filter that allows power line frequencies to easily pass through but block higher frequency noise. Filters, aka power conditioners or line conditioners, are also available as stand-alone equipment.

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  • \$\begingroup\$ Thanks a lot, this sounds about right. Could you shortly elaborate on why using another outlet removes the effect? Does the effect dimnish, or is there a piece of circuitry somewhere that removes the effect? \$\endgroup\$
    – Keno
    Commented Sep 27, 2013 at 16:10
  • \$\begingroup\$ It's hard to say in general. Controlling noise is kind of a black art. Not that the basic principles are mysterious, but a lot can depend on the physical arrangement of the components and how they are interconnected. Distance alone can make a difference. Cables do have parasitic capacitance, inductance and resistance which act to filter noise. Noise, like all electrical signals, will follow the path of lowest impedance. That path includes parasitic components and is dependent on its geometry. If you can get your sensitive equipment far enough away from that path, you should be ok. \$\endgroup\$
    – user28910
    Commented Sep 27, 2013 at 22:25
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It sounds like the power supply on device A is susceptible to noise, and might be poorly designed. Noise can get through power lines, especially for anything that is switching power quickly.

If, and only if, you're certain that proximity has no effect, I'd go for something like an AC power conditioner. This device is relatively inexpensive, but there might be something like it that is medically certified.

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