Magnetometer (noun)

1. An instrument for measuring the strength, direction, or gradient of a magnetic field.
2. A device used to measure the strength of the Earth's magnetic field.

Origin:

From french magnétomètre, from magnét- "magnetic" + -mètre "-meter".

Examples:

1. The geologist used a magnetometer to map the subsurface structure of the area.
2. The space probe was equipped with a magnetometer to study the magnetic field of the planet.
3. The magnetometer is a key instrument in mineral exploration.
4. The engineer used the magnetometer to measure the strength of the magnetic field in the machine.
5. The archaeologists used the magnetometer to locate buried structures.