A Hall Effect sensor such as the (Allegro) UGN3503UA Hall Effect Sensor http://www.jaycar.com.au/products_uploaded/ZD1902.pdf can be used to measure magnetic fields. (The Allegro1302 http://www.alldatasheet.com/datasheet-pdf/pdf/120806/ALLEGRO/A1302EUA.html is an alternative to the Allegro3503).
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A Hall Effect sensor such as the (Allegro) UGN3503UA Hall Effect Sensor http://www.jaycar.com.au/products_uploaded/ZD1902.pdf ($6ea.)can be used to measure magnetic fields. (The Allegro1302 http://www.alldatasheet.com/datasheet-pdf/pdf/120806/ALLEGRO/A1302EUA.html is an alternative to the Allegro3503).
The sensor requires +5V, this is available from the XO's USB connectors.
The sensor requires +5V, this is available from the XO's USB connectors.