Question

Question No 1 (CLO-1) (a) A Wind speed sensor was installed inside a wind tunnel. The sensor was tested and following output data was recorded at different wind speeds: Wind speed Vout (m/s) (V) 0 0.00 2 0.35 4 0.65 6 1.10 8 1.42 10 1.85 12 2.17 14 2.54 Sketch input output graph of the sensor using recorded data and evaluate the following: 1. Linearity II. Sensitivity (b) When a 250-lbs man gets in his car, the car body sinks 1.2 in. What is the spring constant for the suspension system of the car? Sketch TF of the seat while maximum load the seat can take is 350lbs. (c) A toothed-rotor sensor has 24 teeth. Find the rpm if the sensor outputs pulses at 160Hz. Page 2 / 4 a +

Answer 1

transfer function  of the seat which is the ratio of the output (acceleration, displacement, etc.) of the seat to the input as a function of  frequency.

a)

Linearity is the property of a mathematical relationship that can be graphically represented as a straight line. Linearity is closely related to proportionality.

Wind speed is directly proportional to output speed of sensor.

Sensitivity (S) of a wind speed sensor, defined as the relative change of output voltage per unit applied voltage and change in mean wind speed.

Mean wind speed = 56 / 8 = 7 m / s

Wind Speed	Change In mean wind speed (7-wind speed)	Vout   (V)	Relative Change in Vout $\Delta V_{out}$
0	7	0
2	5	0.35	0.35
4	3	0.65	0.30
6	1	1.10	0.45
8	1	1.42	0.32
10	3	1.85	0.43
12	5	2.17	0.32
14	7	2.54	0.37

From second column change in mean speed = 32/8=4=$\Delta U$

From the fourth column average $\Delta V_{out}$ =0.363

Sensitivity $S=\frac{\Delta V_{out}}{V_{in}}.\frac{1}{\Delta U}$

S= (0.363 / 1) x (1/ 4) =0.091

b)

F=kx

F=mg

mg=kx

k= (mg)/x

m= 250lbs g = 385.83 in/s² x=1.2in

k =( 250x385.83) / 1.2 = 80381.25 lbf/in

c)

1Hz=60rpm

Then

Rpm of sensor with frequency 160Hz = 160x60=9600rpm