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Unformatted text preview: E i amplifier filter-12 dB +32 dB 100 Ω 60 Ω E Spring 2010 CEE 291 - Homework 7 Problem 1 A strain gauge – force sensor, which changes its output resistance as it is loaded, forms one leg (R 1 ) of the Wheatstone bridge, page 18 of notes. The sensitivity coefficient of the sensor to loads is 0.5 Ω/N; at no load, the sensor resistance is 500 Ω. The fixed resistance of R 3 and R 4 is 500 Ω. a) For measurements as a balanced (null mode) bridge, how would R 2 vary with load, L, applied to the sensor? b) For measurements as an out-of balance (deflection mode) bridge with R 2 = 500Ω = fixed resistance, determine the bridge output voltage for an input voltage of 10 V and load of 930 N applied to the force sensor. Assume the voltmeter has an input impedance of ∞ so that I g = 0. c) For the conditions in part (b), what is the current flow through the sensor? d) Repeat parts (b) and (c) for R m = 11,625 Ω = input impedance of voltmeter and the volt meter reading = Em = -1.5117 V. As there are unknown currents in each of the 4 arms of the bridge, you will need 4 equations. Em = -1....
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This note was uploaded on 05/04/2010 for the course CEE 291 taught by Professor Hoopes during the Spring '10 term at Wisconsin.
- Spring '10