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Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
Thank you for that wonderful site!
The 'dipping needle" measures the angle of declination for the area in the world you are in. That dip needle was used to find anomalities caused by buried iron objects. Perhaps a good electronic compass held sideways would do.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
I cannot speak too highly of Speake & Co. of Llanfapley in Wales, who produce good quality fluxgate magnetometer (FGM) modules, for which application specific ICs are available, at very reasonable prices.
Their FGM-2 module "consists of two FGM-1 devices moulded into a circular package at right angles to one another, intended for use in field vector magnitude and direction finding systems. It can be used in two dimensional compass systems and in conjunction with an additional FGM-1, in three dimensional systems such as virtual reality and antenna orientation."
The best thing about Speake & Co is that they seem to have just as much time for the little guy as for the granfaloonery of corporations and the organs of the state.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
I consider emf to be measured in Volts I assume EMF to be measured in Tesla
To 'map' a slice of an audio field (spl) a led driven by an amplified microphone capsule with battery and electronics is stuck to the end of a stick. As the stick is waved about the led brightness gives an indication of spl. If a long exposure photo' is taken then a 'map' of spl results. Enhancements include 3x mic/filter/amp with RGB leds for 3-band 'mapping' etc. So maybe a Hall effect probe with a bi-colour led could give a relative +/- intensity map. With 3 sensors mutually 90 degrees to each other, feeding RGB a two dimensional slice of the 3d field could be 'mapped' JUST AN IDEA, I HAVE NOT TRIED IT.
Registered Member #2390
Joined: Sat Sept 26 2009, 02:04PM
Location: Milwaukee Wisconsin
Posts: 381
I would guess that you are referring to one of the devices you see on tv shows like "ghost hunters" and such. That device measures magnetic fields, and they are measured in teslas or T. I have never heard voltage referred to as EMF, however, in most text books on beginning electronics voltage is symbolized by the letter E for electromotive force. Current is usually symbolized by the letter I for intensity. I am not so positive that when these guys on tv say "EMF detector" that they really are called that. They just know the device measures the strength of a magnetic field. I have actually seen the same devices called a MFSM or magnetic field strength meter, but that was an old analog device that had a big whopping needle that bounced around. Nothing like the small digital display models you see on tv. I think in this case the "EMF" is just what these plumbers who chase ghosts call that little box that shows numbers when they wave it around the homes electrical panel.
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EMF
