| Abstract from DBPedia | A proton magnetometer, also known as a proton precession magnetometer (PPM), uses the principle of Earth's field nuclear magnetic resonance (EFNMR) to measure very small variations in the Earth's magnetic field, allowing ferrous objects on land and at sea to be detected. It is used in land-based archaeology to map the positions of demolished walls and buildings, and at sea to locate wrecked ships, sometimes for recreational diving. PPMs were once widely used in mineral exploration. They have largely been superseded by Overhauser effect magnetometers and alkali vapour (cesium, rubidium, and potassium) or helium magnetometers, which sample faster and are more sensitive.プロトン磁力計（プロトンじりょくけい、英語: proton precession magnetometer, PPM）または磁気共鳴型磁気センサは、水素原子核＝陽子（プロトン）の核磁気共鳴を利用して磁場の大きさを計測することを目的とした計測器。 (Source: http://dbpedia.org/resource/Proton_magnetometer) |
