Understanding Half Bridge Strain Values

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In a half bridge strain gauge configuration on a simply supported beam, a negative strain indicates compression in the material. This occurs when one gauge experiences tension while the other experiences compression. The concept of negative strain relates to a reduction in dimension, signifying that the material is under compressive forces. Additionally, when a solid is subjected to uniaxial tension, it experiences a slight reduction in cross-sectional area, leading to negative transverse strain, which is described by Poisson's ratio. Understanding these relationships is crucial for accurately interpreting strain measurements and their implications on force within the beam.
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Hi, I am using a half bridge strain gage configuration on a simply supported beam. If i get negative strain, does that mean I am getting a positive force or a negative force on the beam? I am confused since one gage is in tension and the other is in compression.

Thanks
 
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A negative strain indicates a reduction in dimension, which indicates compression.

When a solid is in uniaxial tension, there is a slight reduction in cross-sectional area, or a negative strain in the directions transverse to the tensile axis. The relationship between (ratio of) transverse contraction strain to longitudinal extension strain is expressed through Poisson's ratio.

http://silver.neep.wisc.edu/~lakes/PoissonIntro.html
 

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