Surface stress meter for thermal or chemical tempered glass(SSM-II) 1. Application The instrument is applicable to non-destructively determine surface stress of the heat-strenthened or tempered float flat glass, and can also be used to measure the surface stress of the chemically ion-exchanged glass. 2. Technical data a. Contact oil: Clove oil with index of refraction at 25℃=1.54 b. Magnification of micrometer eyepiece: 15× c. Min. degree scale of micrometer eyepiece: 0.01mm.