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Confused with dB conversions

  1. Jun 9, 2005 #1

    I´m a little bit confused regarding conversion to dB:

    Regulations for a project I´m on say the maximum magnetic field strength allowed is 60 dBuA/m at 10 m. (here I chose 60 myself for simplicity...)

    So the question is will this correspond to 1 A /m at 10 m (10log[1000000/1]=60 dB)

    or will it correspond with 1 mA / m at 10 m since 20log[1000/1]=60dB.

    should I use 20log or 10 log???

  2. jcsd
  3. Jun 9, 2005 #2


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    What has dB (probably 'decibell') have to do with magnetic field strength...?

  4. Jun 9, 2005 #3


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    It's decibel. I believe you would want to use 20. The 10 is used in power calculations because of the I^2 term in the equations for power, IIRC.

    Since this is out of my realm, I would recommend another opinion. I'll do some searching to see if I can find anything concrete.
  5. Jun 10, 2005 #4
    60dBuA is equal to 1mA. Mr. Garvin is correct, you would use 20Log, 10Log is used for power (or more correctly the ratio of 2 powers). for every additional 20dB, add a factor of ten. 80dBuA is equal to 10mA, etc.

    Electromagnetics, what a concept.
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