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The
Inertial Force Transducer.
The
inertial transducer relies on the action and reaction of internally produced
electromagnetic forces on "voice coils". The reaction force and
the spring force, resulting from the displacement of the internal mass, work together
to produce the resulting axial force on the housing of the unit following well
known formulas, creating a magnification of the magnetic force when the forcing
frequency is above the resonance frequency. A typical force vs. frequency
response is shown in fig. 1. The unit that produced this output is described in
exhibit A.
In order for this type of transducer to produce a force which closely follows
the input current it is necessary to avoid modulation of the magnetic field as
a result of the field produced by the coils. This is obtained by using a
plurality of coils, which produce closely linked opposing fluxes, not only
avoiding flux modulation, but also providing a strong reduction in
inductance. An example of flux modulation is shown in fig. 2 for a unit
using a single coil. Fig. 3 shows the result of a unit with two coils.
A smooth, distortion free motion of the mass is obtained by the use of
flexures. Molded flexures are used in units operating at lower
temperatures, while units operating at 300¡C are outfitted with metal supports.
The closed housing of the inertial transducer can withstand and transfer very
high external forces and therefore is ideally suited to be used in series with
passive elements like engine mounts.
Figure 1
Figure 2
Figure 3
Contact Motran Industries Inc.
Last revised 7/28/03 12:00:32 PM