Calculate Tensile Stress with Strain Gauge

[orla22]

A strain gauge has a unstrained resistance of 120 ohms, gauge factor of 2.0 is connected to steel girder so it experieces tensile stress. If strained resistance of gauge is 120.13 ohm. How do i calculate the tensile stress value?

I have looked all over the internet for equations relating but have not succeded, any help would be great

 

[overt26]

If you look at the link it might help ...

http://en.wikipedia.org/wiki/Strain_gauge"