Consider the cantilever-beam Wheatstone bridge system that has four strain gages (two in compression and two in tension). Which of the follo

Question

Consider the cantilever-beam Wheatstone bridge system that has four strain gages (two in compression and two in tension). Which of the following statements is not true: (a) the change in resistance in each gage is proportional to the applied force, (b) temperature and torsional effects are automatically compensated for by the bridge, (c) the longitudinal (axial) strain in the beam is proportional to the output voltage of the bridge, (d) a downward force on the beam causes an increase in the resistance of a strain gage placed on its lower (under) side. Final Ans: (d) Compression on a lower side gage causes an increase in its resistance.

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niczorrrr 5 months 2021-08-28T10:43:02+00:00 1 Answers 2 views 0

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    2021-08-28T10:44:45+00:00

    Answer:  (b) temperature and torsional effects are automatically compensated for by the bridge,

    Explanation:

    As can be seen, strain gages 1 and 4 are on top of the beam and strain gages 2 and 3 are on the bottom of

    the beam. Therefore strain gages 1 and 4 experience a tensile strain (are stretched) and strain gages 2

    and 3 experience a compressive strain. If the relationship between strain and resistance is linear, then

    under some load F the changes in resistance will be

    R1= R1 + dR1

    R4= R4 + dR4

    tensile(4)and

    R ¢2= R2 -dR2

    R ¢3= R3 -dR3

    compressive. (5)

    when the four strain gages have an equal nominal

    resistance (i.e., R1 = R2 = R3 = R4 = R) then the deflection method Wheatstone bridge equation reduces to the linear equation

    Using known weights, a calibration curve can be established that relates the weight W to the output

    voltage on a digital meter Eo,

    Eo= a0 + a1W , (4)

    where a0 and a1 are some constants. Once an unknown weight is known, an unknown mass or density

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