Re: Gauss meter
GC, funny you mentioned ghost busters. There is a TV crew that goes around (or used to) to haunted houses with all kinds of electronic equipment, acting real scientific. They prefer an inexpensive analog meter which is very sensitive (and very inaccurate as I found when I tested it in my lab). They get all excited when the needle goes up, thinking it is a ghost. Actually, in the old houses, it is usually net current from knob and tube wiring. But hey, the show must go on.
I designed a gaussmeter and also tested everything that came on the market. There are a lot of inaccurate meters out there, mainly because they do not have a flat frequency response. In other words, any 180 Hz or other harmonic will be read three times or more too high. My own meter achieved a very flat response and stayed within 5% up to about 3 kH.
I recommend a triaxial gaussmeter, the Bell 4080, which is about $250, and has excellent accuracy. It reads correctly no matter how you hold it. I use it for the initial survey. Two sources are lessemf.com and magneticsciences.com.
My design, the MSI 95, is a single axis gaussmeter which is useful in locating sources because it is directional and the sensor is on a cord, so it can be used easily. Do not get a one-piece single-axis meter, as you will have to twist your head to read it. A single axis sensor reads correctly only when it reads the maximum.
By the way, I sold my meter business (MSI)and get no kick-back on the new company's sales.
Karl
