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Quiz #3 ME 368 - Engineering Measurements and Instrumentation
Oct 14, 2009, 12:05 – 12:20 pm Fall Semester 2009
Problem Q3-1:
Consider the following circuit:
i) What type of filter is this? (circle the letter of the best answer below)
a. a high pass filter [x/20]
b. a low pass filter
c. a band pass filter
d. a notch filter
e. not a filter at all
ii) Find an expression for the transmission of the filter |Vout/Vin|, as a function of R, L, and ω. Your final expression should not contain any complex numbers in it.
[x/10] Considering this circuit as a complex voltage divider, obtain Vout = Vin*j ωL/(R + j ωL).
[x/10] Computing, get |Vout/Vin| = ωL/sqrt(ω2L2+R2)
iii) If R = 0.1 kΩ, L = 0.01 mH, and f = 1 x 104 Hz, what is |Vout/Vin|?
[x/10] ω = 2*pi*f = 62832 rad/s (intermediate result so don’t round / truncate)
[x/10] Compute |Vout/Vin| = 0.006
[x/10] Leave just one significant digit in above answer
Problem Q3-2:
The voltage divider and the Wheatstone bridge are two circuits that convert resistance to voltage. For use with a resistive transducer, name at least one advantage of one of these circuits over the other.
[x/30] Any of the following:
· The Wheatstone bridge is superior because the measured voltage is generally small owing to the balancing effect. It is easier to measure small changes in a small number than small changes in a big number.
· For equal precision, the Wheatstone bridge is likely to have better linearity than the voltage divider due to less Joule heating of the resistors.
· The multiple resistors in the Wheatstone bridge offer increased sensitivity.
· The multiple resistors in the Wheatstone bridge can be arranged for high sensitivity to one parameter (the parameter one wishes to measure) and low sensitivity to one or more other parameters.
I have neither given nor received, nor have I tolerated others’ use of unauthorized aid on this quiz.
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