The instrument consists of coils a and d, wound on cores / and 3, and
armature 4 mounted on elastic element 2. The change in the inductance
of coils a and d is proportional to the change in the air gaps between armature
4 and cores 1 and 3. This, in turn, is proportional to the compressive
strain of elastic tube 2 and, consequently, to the torque applied to the
lin k acting on the tube.
$4391$SmE,M$