INNOVATIVE GEO-TECHNICAL INSTRUMENTATION

Vibrating Wire Sister bar strain Gauges

MODEL IG - 1201

Innovative series IG 1201 Sister Bars are a modified version of strain gauge model 1200. Sister bars are tied parallel to original re-bars in a structural cage. These measure the actual strain in concrete. A hollow central casing separates the sensing gauge from the concrete while long rebars connected to both ends through modified brackets provide a strong positive bond with the surrounding concrete.

Sister bars may be used in plies, tunnels, foundations pillars and other concrete structures.

The strain gauges have a unique integral magnet design which incorporates a miniature magnet coil assembly positioned inside a stainless steel tube of diameter 15mm. The same tube has a high tensile strength, heat-treated and tempered steel wire stretched between two end blocks. The wire is sealed in the tube by means of a set of double O-rings. This feature, when compared to conventional externally mounted magnet design has the following advantages:

Externally mounted magnet assembly on the other hand is prone to corrosion as it is made in two halves, which are externally clamped on to the tube. This does not ensure proper sealing at the joint. Thus water can seep and with time cause corrosion on the magnet, resulting in failure.

Thermistor provided inside the strain gauge provides the temperature reading.