A strain gauge is a thin strip of metal that is used in measuring of mechanical loads by changing its resistance when subjected to stretching or compressive stresses. Bridge circuits are used in these gauges in order to achieve precise measurements of resistance changes and also compensate the resistance variations due to temperature changes.They have wide uses in engineering profession.

Their operation depends entirely on their physical property of electrical conductance. Electrical conductance on the other hand is a factor of electrical conductivity mostly due to the material property and the geometry of conductor. It is relevant to note that stretching and narrowing conductors within their elastic limit increases their electrical resistance end to end while compressing them makes them thicker hence decreasing their electrical resistance.

As an instrument it is commonly used in measuring of mechanical stresses generated by machines in mechanical engineering applications, research and development. A typical application area of this sensor is in the manufacture of pressure sensors where components like silicon, poly silicon, metal film, bonded foil and metal film are used.

Temperature variation and changes is the biggest challenge faced in manufacture and application of these gauges. The metal strip narrow thickness will expand thermally due to variations in temperatures and this is always interpreted as a strain by the transducer. Thermal expansion of the strips will alter the strip resistance and hence affecting the preciseness of the measurement. To compensate this challenges caused by temperature variations specially made metal alloys are used which self compensate the changes. The other method of countering the temperature variation is by use of Wheatstone bridge having for gauges.

During the construction of this transducer an optimum combination of all affecting factors is paramount. A well constructed transducer should have optimum sensitivity to ensure measurement and detection of even small instances of stresses. It has to be free from temperature effects and other environmental changes. Good linearity and stability together with robustness are also relevant features of a good fabricated gauge.

The size and mass of the sensor should be convenient and preferably small for easy portability. The dynamic nature of the engineering profession application requires measurement tolls that can be applied amply in both static and dynamic measurements. The cost of production and the prices in shop shelves should also be convenient.

Application of strain gauges can be well discussed if divided into their specific areas of use. These transducers can tailor made to measure stresses in steel or stresses in concrete. Applications in measuring pressure in steel include monitoring stresses in the structural steel members of buildings, bridges and supports during and after completion of civil engineering works. They are also used in monitoring tresses in strutting systems foe deep excavations. Application in concrete includes measuring strains in reinforced concrete.

They can be purchased in a whole complete set with all the elements and bridge resistors in one encasing. They are very useful in engineering fraternity for they help detection of stresses that are of vast importance to engineers. Accelerometer