Proton precession magnetometer

A proton precession magnetometer measures magnetic fields using the behavior of protons in a magnetic field. When a strong radio wave pulse is applied, it temporarily aligns the spins of protons in a sample of hydrogen-rich material, like water. When the pulse stops, the protons' spins precess—rotate—at a frequency directly proportional to the magnetic field strength. By measuring this frequency, the device determines the magnetic field intensity accurately. It’s a reliable, sensitive instrument used in geology, archaeology, and space research to detect variations in Earth's magnetic field or other magnetic sources.