1 Define the following terms Gauge factor Poissons ratio ela

1) Define the following terms: Gauge factor, Poisson’s ratio, elastic strain, and Young’s modulus. 2) What is the primary purpose for using a Wheatstone bridge in these experiments? 3) When a weight is put on the end of the beam, which strain gauges from strain gauge 1-5 do you expect to increase in resistance and why? Which ones will decrease? 4) How can a 14-bridge be altered to correct for error due to temperature fluctuations? 5) In general, does the resistance of a conductor increase or decrease with an increase in length?

Solution

1)

Gauge factor : Gage factor is defined as the ratio of fractional change in electrical resistance to the fractional change in length (strain).

Poisson\'s ration : Ration of transverse strain to axial strain

Elastic strain : A form of strain in which the distorted body returns to its original shape and size when the deforming force is removed.

Youngs Modulus : Young\'s modulus is the ratio of stress (which has units of pressure) to strain (which is dimensionless), and so Young\'s modulushas units of pressure. Its SI unit is therefore the pascal (Pa or N/m² or m. ¹· kg.

2) The primary benefit of a wheatstone bridge is its ability to provide extremely accurate measurements (in contrast with something like a simple voltage divider). Its operation is similar to the original potentiometer

4) For 1/2 Bridge strain (2 active gages per wheatstone bridge), the output is double of the 1/4 bridge strain, so the error would be reduced by a factor of two. An alternative solution for 1/2 bridge strain would be to use external excitation, so the power for the wheatstone bridge would not be multiplexed, only the output from the top side of the wheatstone bridge (in this setup the multiplexer\'s relay contact resistance does not affect the measurement.

5) Resistance is directly proportional to length i.e resistance increases as length increases