Veloc. Theory of Oper.

Velocity transducers use the principle of magnetic induction (according to Faraday's Law) to convert the relative velocity of the coil's motion within the magnetic field to voltage. As long as the magnetic field changes, electric current is produced.

Faraday's law of induction states that the electromotive force (emf), the induced voltage, is equal to the rate at which the magnetic flux through the circuit changes. The emf is given by:

(1)     

where:

e is the emf and

[[Phi]]B is the magnetic flux.

It can be shown that the induced voltage is proportional to the magnetic field strength B and the velocity of the coil movement and is given by:

(2)     

where:

Lx is the area of the coil that is exposed to the magnetic field,

x is the height of coils, and

dx/dt is the velocity of the coil movement.

A coil moving in a magnetic field produces a voltage linearly proportional to the coil's velocity since N, L, and B are constant. This proportionality is given by:

(3)     

where:

V is the voltage predicted from a velocity measurement,

Cv is the constant of proportionality, and

dx/dt is the velocity.

Note: If the coil does NOT stay within the magnetic field, non-linear effects will cause the voltage not to be linearly proportional to velocity.