代写MPHY0009 Exam Paper 2022-23帮做R程序

日期：2024-04-11 05:48

MPHY0009 / 2022-23 (Main)

QUESTION 1

Figure 1 The frequency response of a first-order low-pass instrument.

A first‐order low‐pass instrument has a time constant of 20 ms. Find the maximal sinusoidal input frequency (fm) that will keep output error due to frequency response less than 5% (See Fig 1). Show your workings.         [5]

QUESTION 2

In a Wheatstone bridge, leg 1 is an active strain gage of Advance alloy and 120 Ω resistance, leg 4 is a similar dummy gage for temperature compensation, and legs 2 and 3 are fixed 120 Ω resistors. The maximum gage current is to be 0.030 A.

a. Draw the Wheatstone bridge circuit.           [2]

b. Calculate the maximum permissible dc bridge excitation voltage? (Use this value in the remaining parts of this problem)         [3]

c. If the active gage is on a steel member, what is the bridge-output voltage when a stress of 109 N/m2 is applied?          [5]

Given:

- Young’s modulus of steel: 1.9×1011 N/m2

- Gage factor of Advance alloy: 2.1

Show your workings for parts b. and c.

QUESTION 3

Give the schematic of a signal conditioning circuit that would give an output proportional to the displacement measure by a LVDT. Make sure that you capture both the magnitude and the direction of the displacement.            [5]

QUESTION 4

With the help of a diagram describe the frequency response of a piezoelectric sensor. In the diagram, mark the frequency range where you want your measurement variable to lie.     [5]

QUESTION 5

Explain the concept of input impedance of sensors by taking the example of a temperature sensor.             [5]

QUESTION 6

If the foot area of a person is 100 cm2 , calculate the minimum thickness of the rubber shoes that a person wears to be electrically safe when touching a live 240V powerline. Assume that you can ignore the resistance of the skin and body in comparison to the resistance of the shoes.           [5]

Given

- Resistance of rubber is 1013 ohm∙meter

- The dielectric constant is 7

- Permittivity of free space is 8.85 × 10-12 m-3 kg-1 s4 A2

Show your working.

QUESTION 7

Air bubbles are dangerous when using infusion pumps and need to be detected. Describe a sensing mechanism that uses electrical resistance to detect air bubbles.                 [5]

QUESTION 8

Figure 8 A pressure based temperature sensor.

The sensor in Fig. 8 is a temperature sensor. It measures the difference in temperatures of Chamber 1 and 2 by converting the temperature into a pressure. Assuming that the pressure of the chamber is directly proportional to the temperature, explain the working of the temperature sensor.   [5]

QUESTION 9

Figure 9 The circuit for problem 9.

Calculate the voltage VAB in the circuit in Fig. 9.           [10]

Show your working.

QUESTION 10

Brainlab Digital O.R. is a software used to plan brain surgeries based on Computed Tomography (CT) and Magnetic Resonance (MR) images of the brain. Would this be classed as a medical device? Why or why not.             [5]

QUESTION 11

A physiotherapy clinic does a lot of work with patients who have myopathic gait. They have commissioned you to build a simple gait observation tool which can be used to quantify improvements in patients with myopathic gait as they get treated.

a. What is the characteristic of myopathic gait? Why?           [5]

b. What measurements (give any two) would you suggest to monitor the treatment of these patients. How would you measure them?         [5]

QUESTION 12

You are asked to design an audio based navigation system for a blind person. Write three questions you would ask the user of your navigation system before working on the design. Justify.         [5]

QUESTION 13

How would you record the response of the brain to an visual stimulus? (Word Limit: 200 words)        [5]