It is used for elastic deformation measurement and for calculating Young’s modulus of elasticity of wire material.
It is a specially designed apparatus, which is capable of greater degree of sensitivity and accuracy.
It consists of two cast metal rectangular frames hinged together and parallel to each other to allow only vertical relative motion, with a spirit level fixed on a cross-bar pivoted across the frames for noting the reference point.
One frame has a vertical scale, 10-0-10mm with a micrometer head along it reading to 0.01 mm for adjusting the spirit level.
Each frame has a self-centering chuck at its top for holding wires and load hooks at the bottom.
Also included is a ceiling bracket carrying a pair of chucks, a counterpoise weight and a set of two wires, one each of brass and steel.
The relative displacement between the two frames can be known from the micrometer reading after adjusting the bubble of spirit level.