Fluxgate compasses use electronic sensors instead of moving needles to detect Earth's magnetic field.

The fluxgate magnetometer was pioneered in the 1930s by Victor Vacquier at Gulf Research & Development. It gained significant prominence during World War II when it was adapted for Airborne Magnetic Detection (AMD) to locate submerged submarines from the air. The device operates by using two high-permeability magnetic cores wrapped with primary and secondary wire coils.An alternating current is sent through the primary coils to drive the cores into a state of magnetic saturation. When the sensor is exposed to an external field like Earth's, the saturation occurs unevenly between the two cores. This creates a measurable voltage in the secondary coil that is directly proportional to the strength of the external magnetic field along the sensor's axis.Modern fluxgate sensors can detect changes as small as 10 picoteslas, which is roughly 5 million times weaker than Earth's total magnetic field. This extreme sensitivity is why they are essential for the Magnetospheric Multiscale (MMS) mission launched by NASA in 2015 to study magnetic reconnection. Unlike mechanical compasses, these sensors provide continuous digital data streams that are vital for the inertial navigation systems used in aerospace engineering.