Proving Ring are used for load measurements and are used in the outfits of a number of Soil/Cement & Bitumen Testing Equipments like Direct shear Test Apparatus.Triaxial Shear Test Apparatus, C.B.R. Test, Uncontained Test, and Marshal Test etc.
Proving rings can be designed to measure either compression or tension forces. Some are designed to measure both. The basic operation of the proving ring in tension is the same as in compression. However, tension rings are provided with threaded bosses and supplied with pulling rods which are screwed onto the bosses. - See more at: http://www.aticoexport.com/products/proving-ring/#sthash.e1O3gX3t.dpuf