Transcripts of fluxgate_ipod_lg [beeping, computer sounds] [humming, computer sounds] [music] Narrator: A fluxgate magnetometer works essentially like a compass. But, instead of a spinning needle, electromagnets are used to measure magnetic fields. To build one, we start with a bar of ferromagnetic metal. If you wrap a coil of wire around the bar and run an electric current through it, the bar becomes magnetized and generates its own magnetic field. Reverse the current, and the field reverses direction. If you do this over and over again, you can see that the two directions cancel each other out. However, when an external magnetic field is present, the two directions are thrown out of balance, allowing you to measure the external field. Finally, by combining multiple fluxgate sensors, you can measure a magnetic field in three dimensions. [music] [beeping] [beeping, silence] [silence]