Final Exam: 11 May 2001, Friday, 10 AM

Transcription

1 Spring 2001 BE 3600 BioInstrumentation Final Exam: 11 May 2001, Friday, 10 AM ACTUALLY ADMINISTERED IN CLASS This exam: Consists of 12 questions, Score from this exam will determine % of your grade, You will have 2 hours to complete the exam, Closed boos, closed notes, but use of calculators is allowed, Please mar your answers on the COER SHEET, Do not forget to write your name. TEST FORM CODE: YOUR NAME: ANSWERS: GOOD LUCK! Page 1 of 17

2 QUESTION 1 A capacitive sensor is being used to measure the thoracic depth to monitor the respiratory activity. A circuitry is formed as shown below where the x is the distance between the plates of the capacitor, hence the thoracic depth. Determine the equation for the output voltage, C. A) C C X 0 in B) εa C C X + εa 0 in C) C in C0 X C X + εa 0 D) C in X X + εa E) C C0 X + εa in CORRECT ANSWER IS "C" C X 0 Page 2 of 17

3 QUESTION 2 Tip of an electrocautery instrument has a radius of curvature of r 1 mm. It is specified that the electrical arc to cut the tissue will be obtained with 300 olts, when the tip is 1 mm away from the tissue. If the current flowing through the device is 5 nano amps, what is the cross sectional area of the arc current? (You can assume that it taes 100 nano-seconds for electrons to cross the gap). A) mm 2 B) mm 2 C) mm 2 D) mm 2 E) mm 2 CORRECT ANSWER Page 3 of 17

4 QUESTION 3 Input / output relationship of a sensor is given as follows: y[] (0.5) y[-1] + u[], where u[] is the input, and y[] is the output. If the input u[] is a unit step, determine the output y[] A) B) C) D) E) [ ], for 0 y [ ] 2, for 0 CORRECT ANSWER y 2 1 [ ] 2, for 0 y [ ] 1, for 0 y 2 1 [ ] 1, for 0 y + 2 Page 4 of 17

5 QUESTION 4 A capacitive pressure transducer is setup as shown below Where u( is a step function, R 1 MΩ, C1µF (fixed during the tes If we sample the system with T 1 milli-sec time steps, what is the discrete time output of this system ( out []) A) OUT [ ] e, for 0 B) [ ] 1000 OUT e, for 0 CORRECT ANSWER C) OUT [ ] 1 e, for 0 D) [ ] OUT e, for 0 E) [ ] OUT + e, for 0 Page 5 of 17

6 QUESTION 5 Impulse response of a sensor is given as follows: 2, t h( 0, t < 1 1 When an unnown signal x( is applied to the input, following output was observed: t 4(1 ), t y( 2 0, t 2 < 2 Determine x( A) 2, t x( 0, t < 1 1 B) 1, t < 2 x( 0, t 2 C) 2, t x( 0, t < 2 2 D) 1, t < 1 x( 0, t 1 CORRECT ANSWER E) 4, t x( 0, t < 2 2 Page 6 of 17

7 QUESTION 6 A patient's audiology report shows the response of her ear is follows: Which filter shown below would restore her hearing to a flat spectrum? CORRECT ANSWER IS "C" Page 7 of 17

8 QUESTION 7 A flow sensor was designed using the principles of thermo-dilution method. Its output is sampled at T 1 second time steps. Incoming blood is at 37 C, and has a density of 1 gram / cm 3, and specific heat of 1 cal / C - grams. If the flow is at 1 cm / sec, heating element has a resistance of 1 Ω, the distance between the heater and the temperature sensor is 3 cm, and the cross sectional area of the artery is 1 cm 2, find the relationship between the output temperature and the current on the heating element (note that 1 calorie 4.2 Watts). $ I [ 3] A) Temp[ ] 37 C + x B) Temp[ ] 37 $ I C + 2 [ 3] 4.2 CORRECT ANSWER $ I [ 300] C) Temp[ ] 37 C + x D) Temp[ ] 37 $ I C + 2 [ 300] 4.2 $ I [ ] E) Temp [ ] 37 C + x Page 8 of 17

9 QUESTION 8 A piezo-electric transducer wors with the following equation g P, where is the voltage on the transducer, P is the pressure, and g is a constant and equal to 1. This transducer is used for ultrasound imaging and can simply be modeled as a capacitor, C 1 µf. If the entire system is configured as shown below, what is the pea amplitude of the voltage on the transducer, C (You can neglect the attenuation in the tissue. Reflection coefficient for the tissue-bone interface is given as Γ 0.5. oltage source generates a voltage of 0 cos (ω, where f 100 KHz, and 0 10 olts. Distance between the transducer and the bone is 7.5 mm. Assume that the speed of sound in tissue is 1,000 meters per second.) A) m B) 318 m C) m D) 159 m E) 79.5 m CORRECT ANSWER Page 9 of 17

10 QUESTION 9 A pneumotachograph is an instrument to measure the respiration of a patient and shown in the diagram below. Pressure sensors P 1 and P 2 have gain of 1, i.e. P (voltage output is equal to pressure inpu. These two transducers are placed on either side of a fine mesh with resistance to flow R. Determine the expression for OUT (. A) OUT Ramp B) OUT Unit Step C) OUT -(P 2 -P 1 ) D) OUT Φ( E) OUT Respiratory olume (CORRECT ANSWER) Page 10 of 17

11 QUESTION 10 A diode can be used as a temperature sensor. Relationship between the current and voltage is given as follows: I q E g Ae T where I is the current, is the voltage, E g and are constants and T is the temperature. Find the output of the circuit shown below. A) OUT q E g + T 1 Re CORRECT ANSWER A 1 B) OUT t ln + Eg q RA C) OUT 2 + ARe q E T g 2 D) OUT t ln + Eg q RA 2 E) OUT t ln + E g + 1 q RA Page 11 of 17

12 QUESTION 11 Filter shown below is running with input signal sampled at T 1 milli-second time steps. What frequencies are removed from the input signal. y[ n] 7 0 x[ n ] where x is the input, and y is the output. A) 50 Hz and 60 Hz B) 125 Hz and 250 Hz CORRECT ANSWER C) 50 Hz D) 60 Hz E) 60 Hz and 180 Hz Page 12 of 17

13 QUESTION 12 A transthoracic impedance monitor utilizes DC excitation to measure the chest impedance. Find out the voltage drop on one of the electrode-electrolyte interfaces ( TE ) if the excitation is I 0. A) TE HC + I 0 (C D +R D +R S ) B) TE HC + I 0 ( 1/C D + R D +R S ) C) TE HC + I 0 (j/c D + R D +R S ) where j 2-1 D) TE HC + I 0 (R D +R S ) CORRECT ANSWER E) TE Page 13 of 17