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Hi Edgar,
in principle, yes. But:
The question is on how much improvement you
would get, compared to a simple induction loop. A loop responds to the time
derivative of the field, so doesn't respond to DC and very low
frequencies. That's where sensors which respond to the field itself are
needed (eg compass needles, Hall effect, fluxgates, NMR, squids). For example,
the noise of a fluxgate is more or less flat with frequency, and there is a
crossover frequency above which the simple loop wins (usually around 100
Hz, depending on factors like the size, copper mass, or ferrous
core of the loop).
A proton NMR magnetometer with a large enough
sample is sensitive at DC, and has the additional advantage of absolute
calibration referenced to the NMR Larmor frequency. But it actually responds to
the integral of the field, so SNR falls off more rapidly at with frequency.
Superconducting quantum interference devices
(squids) have been used as very low noise magnetometers up to a several 100 kHz.
But this makes sensse only in a shielded room. In the open, atmospheric
background noise dominates by orders of magnitude, and a copper coil of less
than a square meter is able to provides ample SNR at
VLF. Narrowband resonant matching doesn't improve the SNR from the coil
itself (induction voltage vs resistive noise), but it helps to bring
down the noise contribution from the attached preamplifier.
Best 73,
Markus
Sent: Sunday, April 27, 2014 7:05 AM
Subject: LF: Magnetometers
Possibly a silly question but,
Is it possible to detect
low frequency electromagnetic waves with
Fluxgate or Proton
Magnetometer?
e.g. waves with frequency of 8 kHz to 29
kHz?
Regards, Edgar
Moonah, Tasmania.
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