Exchange field noise voltage at various locations

[Prospector Paul]

Hi, I'm new to prospecting & metal detecting, but I've designed a metal detector & built a few versions. I'm interested in exchanging field noise voltage density per m^2 (nV/√Hz/m^2) measurements at various locations? I don't have much so far, just a few locations out here in the noisy city, but hopefully within 2 to 3 months I'll take measurements at various Southern California wilderness locations. The method I'm using to measuring the noise is a low noise op-amp, LT1028A, typically set to a measured confirmed gain anywhere from about 100 to 1000, connected to a coil. For now I'm using a single turn 1 meter OD loop. The op-amp output goes to an oscilloscope that displays a voltage spectrum. If for example the scope is set to 400us/div and each FFT sample for 10 divisions is 4ms, then to get the nV/√Hz I divide the spectrum noise voltage for a given frequency by 1/sqrt(4e-3 seconds). And of course I divide that answer by the single turn coil area, m^2.

I appreciate it! You can send a private message if you prefer.

 

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