A torque-arm load cell carries a foil strain gauge with resistance and gauge factor

PHYSICS · Multi-part · Fermi University Physics · Electronics, Instrumentation & Communication · Sensors, detectors and experimental instrumentation · Sensors, detectors and experimental instrumentation

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Problem

A torque-arm load cell carries a foil strain gauge with resistance R=120 ΩR = 120\,\Omega and gauge factor GF=2.1\mathrm{GF} = 2.1. Under a test load the gauge experiences a tensile strain ε=250 με\varepsilon = 250\,\mathrm{\mu\varepsilon}. The bridge excitation is Vex=12 VV_{\rm ex} = 12\,\mathrm{V}. ((a)) Calculate the fractional resistance change ΔR/R\Delta R/R. ((b)) Calculate the output of a quarter bridge (one active gauge). ((c)) Calculate the output of a half bridge in which a second, matched gauge on the opposite face experiences −ε-\varepsilon. ((d)) Calculate the output of a full bridge with four such gauges arranged so all four arms are active.

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