détecteur rotatif de champ électrique

CONT: Circuit of electric field measurements of thunderclouds. ... The electric field mill is a device based on electrostatic induction. It consists of one or two electrodes which either rotate in an electrostatic field or become periodically exposed to a field by rotating vanes. Fig.46 illustrates a cylindrical field mill which consists of two cylinder halves that are electrically insulated from each other. An electric motor rotates the two halves in the electric field to be measured so that they become alternately exposed to both the positive and negative direction of the field. The result is that an alternating (ac) signal is generated across the two halves which can be easily amplified. ... Although not commonly used, the cylindrical field mill has the advantage that when mounted in a fixed position it can also indicate the direction of the field. This is accomplished by measuring the phase shift of the ac signal relative to the orientation of electric fields need to be measured.
CONT: The device normally used to measure atmospheric electric fields is a type of sensor called an electric field mill. It can be used on the ground to gain information about the field aloft, or it can be flown on an airplane or balloon. Thirty-one ground-based field mills at Cape Canaveral Air Force Station and the Kennedy Space Center are used to measure the electric field just above the surface of Earth, in the lowest meter of the atmosphere, and determine if it meets the safety levels specified in the Lightning Launch Commit Criteria. The small, cylindrical field mill is mounted upside down.