The design is an improved version of stress meter developed for the U.S.B.M. for measurement of stresses in bore holes of 38 to 42mm size holes at different orientation and at different depth. Two designs are available one for soft rock & one for hard rock.
- Model 2270 is suitable for soft rock application like coal etc. This stress meter basically consists of a pretension wire in a cylindrical cell flattened at the top to suit a wedge and platen assembly. In soft rock design platen has a bigger surface area to make proper contact with rock. In the stress meter installation the wedge is pulled from outside to give a grip to stress meter and platen inside the hole to get a required tension to vib. wire. Setting tool is withdrawn after installation. Further change in tension of wire will give the change in stress in bore hole.
- MODEL SME 2280: This design with smaller platen area is suitable for hard rocks. This also has a cylindrical proving ring of high strength stainless steel with a wedge and platen assembly. Cylindrical body consists of a pretensions vibrating wire with a electromagnet which make the wire to vibrate when a pulse voltage is fed to coil through readout unit model SME 2460-S. Which intrun gives a frequency output display depending upon the variation in length of wire due to change in tension of wire under stress. Readout unit also capable of displaying the signal in time period, micro strains and also direct in engineering units i.e. kg/cm².
