- Device for measuring magnetic fields. A network of magnetographs has been installed all over the Earth for decades, yielding huge amounts of data, and versions of these instruments have been sent into orbit and to other planets since the 1960s.
- An instrument which detects and records a varying magnetic quantity, especially a magnetic field.
- An instrument which detects and records a variations in the earth's magnetic field.
- An instrument which detects and records variations in the magnetic field of a celestial body, such as the sun.