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Quick Question

  1. Sep 6, 2006 #1
    Dumb question...but I don't know the answer.

    Is there a way to determine if a piece of metal will cause electronic interference? Is it true only for ferric metals, or can any type of metal cause transmission problems?

    Cya later, alligator
     
  2. jcsd
  3. Sep 6, 2006 #2
    Here is another one for Berkeman or Chroot:

    What is a 'monolithic capacitor' ?

    I guess this is a picture of a 'monolithic capacitor'......

    [​IMG]

    Are they any different from a regular capacitor?

    Here is the site w/ different ones:

    http://www.tedss.com/

    It looks like it is just one 'type' of many capacitors avaiable. What's the difference?
     
    Last edited: Sep 6, 2006
  4. Sep 6, 2006 #3
    Third question, what is meant by "surface mount technology" (SMT)?

    It seems that anything on a circuit board would be 'surface mounted,' no?
     
  5. Sep 6, 2006 #4

    Gokul43201

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    A monolithic capacitor typically has a ceramic dielectric with the electrode metal directly deposited on the sides of the ceramic pill. I think multilayer ceramic caps are also refered to as monolithic.

    Just built a circuit with DIP and radial lead components. It's a PCB - it has no SMD components! What's specific to the SMDs is the lead geometry - the ends of the leads are parallel to the ground plane (and they're flat as oppsed to say, cylindrical).

    Need more info on Q1
     
    Last edited: Sep 6, 2006
  6. Sep 6, 2006 #5

    Bystander

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    Just by itself, it isn't going to generate interference; when you say "transmission problems," you mean "blocking a signal?" Any conductor is capable of blocking signals, sea water, graphite, metals --- signal frequency, and metal thickness, area, and geometry, plus the specific conductor's physical properties (conductivity, magnetic susceptibility, and a couple other things that escape me at the moment) come into play very quickly as far as calculating signal loss. Help?
     
  7. Sep 6, 2006 #6

    berkeman

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    Just to add a little bit about your first question. I'll assume that you mean interference with EM signals like cell phone transmissions or HAM radio. The main issue is the size of the piece of metal compared to the wavelength of the EM signal. If a single piece of metal is much smaller than a wavelength (say 1/10), then no, it will not influence the pattern of the EM much. So a trash can sitting in front of a 10m HAM Yagi antenna is not going to affect the DX (range) much. But if you have a larger piece of metal, or an array of smaller ones, then yes, that does affect how much of the EM signal gets through.

    There is also the issue of skin depth, which varies with the EM frequency and the conductivity of the piece of metal. The skin depth is something like (I forget the exact definition) the depth into the metal where the EM field has fallen off to 1/e of its original magnitude. As long as the metal sheet is several skin depths thick, it will prevent the EM signal from getting to the other side (it is reflected and partially converted to heat).

    Is there a specific example that you have in mind? Maybe setting up a WiFi network in your house, and wondering why the signal doesn't go around corners too well?

    Mike
    KI6EGL
     
  8. Sep 6, 2006 #7
    I put in a small piece of metal reinforcement on a small UAV at work and I wanted to know how to figure out if it would cause transmission issues. The frequencies are 900 MHz and 2.4 GHz. There is also an on-board magnetometer.
     
  9. Sep 6, 2006 #8

    berkeman

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    Yeah, multipath is always a problem for the ISM bands 2.4GHz (microwave oven frequency) and 900MHz. How close are any antennas? Can you post a sketch?
     
  10. Sep 6, 2006 #9

    Gokul43201

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    What's the sensitivity of the magnetometer and what field is it trying to measure? What is the metal (may need complete alloy spec) , and what are its dimensions? How far is it from the magnetometer and what is its orientation?
     
  11. Sep 6, 2006 #10
    I don't know the specs of the magnetometer. It measures the earths magnetic field to get a position estimation for the autopilot sensor.

    The metal I put in there is brass, but Its at the very least half a foot away (I think?). It's about 1.5" x 1" rectangular and oh, I don't know..two or three sheets of paper thick. It is flat on the wing, and so is the mag. So they are both planar I suppose.
     
  12. Sep 6, 2006 #11

    chroot

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    Monolithic capacitors are those which are not integrated onto a chip. They are sometimes also called 'discrete' capacitors.

    Surface-mount devices have leads which are soldered to pads on one side of a circuit board. The SMT mounting method replaces an older technology called "through-hole," in which holes were drilled into the PCB, and leads from device put through the holes and then soldered on one of both sides of the board.

    As you can imagine, SMT is much more efficient in terms of board space, because components mounted on one side of a board do not interfere with components mounted directly on the other side.

    - Warren
     
  13. Sep 6, 2006 #12

    Gokul43201

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    Assuming its not some weird (high nickel or such) brass, here's a rough estimate of the error in measuring field at the worst possible orientation (i.e, magnetometer is in the plate's magnetic "shadow") : 100 ppm

    Edit: Can do a better calculation if reqd...may take several minutes.
     
    Last edited: Sep 6, 2006
  14. Sep 6, 2006 #13
    AHHHHHHHHHHHH, Great thank you! What a nice post!
     
  15. Sep 6, 2006 #14

    Danger

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    I didn't even have time to read all of the responses to this, and this is for sure not within my technical knowledge, but I can definitely say that my 'bunny ears' TV antenna worked better with some Reynold's Wrap aluminum foil clamped on.
     
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