Electromotive force (E.M.F.) is generated along an explorer, when he is crossed by the variable magnetic field. And, vice versa, when an explorer moves through the magnetic field, along him generated E.M.F. (fig. 1), determined from next correlation:
E = - d(Nф)/dt,
where d(Nф)/dt is speed of change of coupling of streams .
Fig. 1. Electromagnetic transformation
Fig. 2. Inductive transformation
Fig. 3. Transformation of magnetic resistance, used in a differential transducer with an arcwise-changing output
Inductive transformation is shown on a fig. 2, where the self-induction of spool changes in accordance with the change of measurand. The change of inductance can be carried out by motion of ferromagnetic mandrel into a spool or by bringing of external changing stream in a spool with an immobile mandrel.
Transformation of magnetic resistance is shown on a fig. 3, on which chainlet of resistance between two or more changes spools (or by separate parts of one or a few spools) depending on variations of measurand. When to the system of spools an alternating current is put, then, the change of measurand is transducer in the change of output tension.
Traditionally, electromagnetic measuring transducers are subdivided into transducers for measuring static magnetic fields and transducers to measure AC electromagnetic fields. Moreover a number of converters can be used to measure both permanent and alternating magnetic fields. For example, a fixed inductor can be used for measurements in variable magnetic fields, and when you move that coil to make measurements in static magnetic fields. Hall sensors can also be used to measure both DC and AC magnetic fields.