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Tri-Mag Tester |
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Taylor, T. |
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British Geological Survey, Edinburgh, UK |
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A geomagnetic observatory regularly requires the fabrication of bespoke parts, brackets or equipment installed close to, or even touching instrument sensors. Metals and components used for this can sometimes be contaminated (cheap brass), disguised (plated steel), or changed by their fabrication (for example welded or cold-worked austenitic stainless steel). Materials expected to be ‘non-magnetic’ can sometimes be slightly tainted, affecting observatory data if installed. Passing a test sample over a compass is not very responsive, and doing the same over a zeroed fluxgate theodolite sensor is very sensitive to background interference and changing field. Therefore, a simple means of testing small components in a noisy lab environment was sought. The Tri-Mag arranges three miniature fluxgate magnetometers about a tube; this compensates for external fields and creates a sensitive gradiometer inside. The outputs from each sensor then pass through a series of analogue filters to remove noise and boost sensitivity, producing an audible/visible output on detection of a magnetic material. |
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Instrumentation |
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poster |