When armature 1 is vibrated by the app lied dynam ic force F ,
bending its supporting flat springs, the air gap between the
armature and the core of coil 2 varies. Coil 2 has two windings:
primary a and secondary b. This m otion changes the coefficient
of m u tu a l inductance of coil 2. The coefficient is used to measure
force F since when prim ary w ind in g a is supplied by direct
current, the a -с voltage in secondary w in d in g b, measured by
voltmeter 3, is proportional to the frequency and am p litu d e of
v ibration of armature 1, which depend on force F being measured.
$4385$SmE,M$