Rotational-type magnetic sensor

The present invention concerns a magnetic field sensor suitable to continuous measurement for magnetic fields at places where installation of semiconductor-type magnetic field sensors is difficult because of high temperature and presence of radiation, for example, the inside of a vacuum vessel of a thermonuclear device. One or more rotatable coils, a power source for supplying current to the coils and a means for measuring voltage induced by the coils are disposed to measure magnetic fields for a long period of time. Since intensity of magnetic fields is measured while rotating coils using the electromagnetic force caused by the magnetic fields to be measured, driving devices for the rotational movement such as air pipelines and a motor for driving coils are no more necessary, thereby enabling to simplify the structure of the sensor. In addition, measurement for steady magnetic fields can be conducted at high temperature, in strong magnetic fields or under radiation where an ordinary motor does not function. (N.H.)