EMC Question of the Week: September 23, 2024

Plot of electric field strength vs frequency showing a limit line at 40 dB microvolts per meter.

Which of the following is equivalent to 40 dB(μV/m)? 

  1. 40 μV/m
  2. 40 dB
  3. 100 nA/m
  4. -80 dB(V/m)

Answer

The best answer is “d.” 40 dB(μV/m) is an electric field strength equal to 100 μV/m, which is 10‑4 V/m or -80 dB(V/m). 40 dB is a ratio, not a field strength. 100 nA/m is a magnetic field strength.

In general, units of dB(μV/m) can be converted to dB(V/m) by subtracting 120 dB.

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