MECHANICAL STRAIN GAUGE Wedge and screw magnification Simple mechanical lever magnification Compound magnification system 1. Berry strain gauge 2. The Tinius Olsen strain gauge Compound lever magnification 1. Huggenberger extensometer 2. Porter- Lipp strain gauge Magnification by rack and pinion Combined lever, rack and pinion magnification

WEDGE AND SCREW MAGNIFICATION

-contn.. It is simply a triangular plate with its longer sides related by a 1:10 slope. When inserted between two shoulders the extensions could be detected to the nearest 0.05mm.

WEDGE AND SCREW MAGNIFICATION

-contn Developed by Howard (1885) The Howard strain gauge measurements can be made to the nearest 0.0025mm with a probable accuracy of 0.005mm under normal operating conditions

Popular Wedge gauge Helps in Crack detection, Flatness detection 0.5-10 mm

SIMPLE MECHANICAL LEVER MAGNIFICATION

Capp’s divider

The simple lever strain gauge gains its magnification factor by a suitable positioning of the fulcrum. The magnification of this type of gauge is unlimited actually however, the magnification ratio is perhaps limited to 10to20,because of the limitations placed on the gauge by size and weight. The gage length of Capp’s divider is 5 cm and strain is 10:1 on graduated scale.

For this gauge large volume must be available directly over test area. In case of large structures of large structures small hole is bored in structure into which is secured to hold the strain gauge during loading of structure.

APPLICATION Capp’s divider is generally used for determination of the yield point and yield strength of materials under tension test.