magnetic field effect

Discussion in 'Digital Darkroom' started by diegobuono, Aug 4, 2014.

  1. Hi all, When not in use I would like to rest my hasselblad flextight 646 between the TV set and audio speaker, I know it should be not
    used near magnetic fields but I'm thinking to myself if the storage that way could dause some problem to the mechanics (magnetization
    of some parts), I suppose this is not a problem, the scanner itself has some magnetic part (where it catchbthe film holder) but may be
    someone knows more. Thank you in advance.
    Diego
     
  2. I think the magnetization of ferrous material placed near (domestic) loudspeakers is grossly exaggerated.
    It probably grew out of the days when it might have distorted a TV picture under certain conditions, or as a precaution warned against placing magnetic tapes near speakers, but given the field strength is inversely proportional to the square of the distance, the practical effect of loudspeaker magnets on external objects is negligible enough to be ignored. It will affect something like a compass needle but that's about it.
     
  3. The type of TV, the size/type of the speaker and distance to each will determine the effect on the flextight over time.
    A few weeks to a few months will most likely have no noticeable effect a few years might.
     
  4. The magnetic field is inversely proportional to the 4th power of separation. The effect on electrons in a CRT is a lot lot more pronounced than aligning domains in a steel spring or conduction in a semiconductor. That said, the magnets in floor speakers (e.g., subwoofers) are pretty large and powerful. I wouldn't store a mechanical camera or lens on top of a speaker for that reason or the vibrations. A pair of 3" speakers easily affected the color of an old CRT set at a distance of over 8". There's no effect on LCD screens.
     
  5. [[I wouldn't store a mechanical camera or lens on top of a speaker for that reason or the vibrations.]]
    Just to note: I believe the OP is talking about a scanner.
    http://www.photo.net/digital-darkroom-forum/00cRHc
     
  6. Even small speakers can create enough EMI to cause problems, but it's usually easily resolved by moving equipment and cords/cables around a bit.
    Last week AT&T switched our phone/ISP to U-verse, which included a new modem. For awhile I was certain the new modem was produced enough RFI/EMI to interfere with the LCD TV. But the culprit turned out to be a coax cable that had been moved slightly so that it was resting directly against a small external computer speaker. Moving the cable about six inches fixed the problem.
    With some installations it's impossible or impractical to avoid proximity of devices. Often EMI/RFI can be minimized by using good shielded cables and simple clamp-on ferrite chokes. The effect of ferrite chokes can usually be enhanced by looping shielded cables/coax at least once through the chokes. Most computer and monitor type ferrite chokes don't do that, so occasionally it helps to add another choke to both ends.
     
  7. Thank you for your prompt reply, anyway it is unclear to me if in your opinion resting the scanner near te speaker and LCD TV could
    affect it functionality. I want to clarify that is only when the scanner is not in use that it rest there, in fact when Imuse it I move in another
    position, where I have a comfortable desk and enough room to operate. This is in another room of my house (unfortunatly I can not
    permanently leave the scanner on that desk).
     
  8. Somehow the thread got diverted to cameras. There's nothing in a scanner likely to be affected by a magnetic field. Any digital device can cause interference with consumer electronics, although I've not seen it on my television or computer. If interference occurs, it can travel through household wiring or space. However, a scanner may be particularly sensitive to vibration, considering the slow, line-by-line scan. If the speaker is off, I see no problem using it to support the scanner, besides aesthetics.
     

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