One arm of a strain-gauge bridge is closed by a load resistor at room temperature

PHYSICS · Subjective · Fermi University Physics · Scientific Practice & Experimental Methods · Electronics, Instrumentation & Communication · Feedback, operational amplifiers and analogue signal processing

Measurement and Method, Ch Designing the measurement: noise, averaging, null and differential methods

Problem

One arm of a strain-gauge bridge is closed by a load resistor

R = 47\,\mathrm{k\Omega}

at room temperature

T = 293\,\mathrm{K}

. The amplifier that reads the bridge has a bandwidth

\Delta f = 8.0\,\mathrm{kHz}

. Estimate the Johnson (thermal) noise voltage that this resistor contributes in that bandwidth, using

v_n = \sqrt{4k_{\rm B}TR\Delta f}

with

k_{\rm B} = 1.38\times10^{-23}\,\mathrm{J\,K^{-1}}

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