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CONT316 Examination – 2018/19
DO NOT REMOVE FROM EXAM VENUE


Plymouth University

TIME ALLOWED Two hours

DATE

TIME

FACULTY Science and Engineering

SCHOOL Engineering

ACADEMIC YEAR 2018/19

STAGE Three

INSTRUCTIONS TO CANDIDATES:












Candidates are not permitted to look at the examination paper until instructed
to do so.



MODULE CODE: CONT316 Examination
MODULE TITLE: Systems, Instrumentation and Control

Answer ALL questions.


Semester 2 Exam
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CONT316 Examination – 2018/19



Q1. (a) The fundamental SI units for use in mechanical technology is mass (M),
length (L) and time (T). Express the following quantities in terms of
fundamental units M, L and T.

(i) Speed

(ii) Power

(iii) Energy (6 marks)

(b) Describe the difference between accuracy and precision in an instrument.
(4 marks)

Q2. (a) A pressure gauge of range 0-10 bar has an inaccuracy of ± 2% of the
full scale reading. Calculate the maximum error in the reading.

(2 marks)

(b) Briefly describe the workings of a potentiometric transducer.
(4 marks)

(c) If a transducing spring deflects 0.04m when subjected to a force of 8KN,
find the input force for an output displacement of 0.08m.
(4 marks)

Q3. (a) Define sensitivity in an instrument.
(3 marks)

(b) Determine the measurement sensitivity of a thermocouple with the given
input and output readings:

Input (degrees) Output (mV)
200 2
400 4
600 6
800 8
1000 10

(5 marks)

(c) Define the setup of a thermocouple thermometer.
(2 marks)

(Over…/)
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CONT316 Examination – 2018/19

Q4. (a) Define and explain the principles of a restriction flow sensor.
(4 marks)

(b) Define the gauge factor (GF) of a metallic strain gauge and calculate the
change in a nominal wire (metallic) resistance of 120Ώ that results from a
strain of 1000 mm/m.
(4 marks)

Equation to be used:

GF =
ε
ΔR/R

(c) Briefly describe the application of pitot-static tubes.
(2 marks)



Q5. (a) Define and explain the principles of accelerometers.
(3 marks)

(b) By equating Newton’s second law and Hooke’s law show that =

∆.
(3 marks)

(c) The acceleration in the mass-spring system is defined as: =

∆

Where K = Spring constant in N/m

m = Seismic mass in Kg

∆x = Spring extension in m


Calculate the maximum measurable acceleration for an accelerometer having a
seismic mass of 0.03 Kg and a spring constant of 2.5 x 103N/m. Maximum mass
displacement is ± 0.025 m.
(4 marks)








(Over…/)

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CONT316 Examination – 2018/19

Q6 (a) Draw the circuit diagram of a non-inverting operational amplifier when it is
used for signal amplification in instrumentation defining all relationships.
(4 marks)

(b) An inverting operational amplifier is required to produce an output that
ranges from 0 to -3V when the input goes from 0 to 80mV. By what factor
is the resistance in the feedback arm greater than that in the input?

Equation to be used:
0

= −2
1

(3 marks)
(c) Define the phenomenon of piezo-electric effect.
(3 marks)

Q7. (a) The general form of a second-order control system is given as follows:

()
() = 22 + 2 + 2

The time response of second-order system depends on the value of damping
factor (ζ). Sketch the typical response for a step input for an under-damped
second-order control system outlining the rise time, settling time, peak
overshoot and peak time.
(4 marks)
(b) Define each parameter in (a) above.
(4 marks)

(c) A system has an input voltage of 12V which is suddenly applied by a
switch being closed. State the input as an s (Laplace Domain) function.
(2 marks)

Q8. Deduce the system transfer function relating C(s) to R(s) for the block
diagram shown in Figure Q8.
(10 marks)

Figure Q8
(Over…/)
R
G1 G2
F
H
G3
C +
ε
_
+

+
R(s)
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CONT316 Examination – 2018/19

Q9. (a) Define a stable control system in terms of system poles and zeros. Sketch
the poles and zeros on the s-plane.

(3 marks)
(b) The characteristic equation for a closed loop system is given by:

F(s) = s5 + 2 s4 + 2 s3 + 4 s2 + 11 s + 10 = 0

Using the Routh-Hurwitz array, determine the stability of the system.
(7 marks)


Q10. (a) Find the Laplace transform () of () given below and hence find the
output ().

() = 18̈ − 7̇ + 2 ; (0) = 3, ̇(0) = 0
(5 marks)
(b) Find the Inverse Laplace transform of:

() = 1(−7)(−3)
(5 marks)

[Note: () = − ℎ () = 1
+
]





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