CORK INSTITUTE OF TECHNOLOGY
INSTITIUID TEICNEOLAIOCHTA CHORCAI
Autumn Examinations 2009/10
Module Title:
Module Code:
PHYS 6008
School:
SCIENCE
Instrument Measurement Principles C/A
Programme Title:
Bachelor of Science – Applied Physics and Instrumentation, Year 1
Honours Bachelor of Science – Instrument Engineering, Year 1
Programme Code:
SPHYS_7_Y1
IE1
External Examiner(s):
Internal Examiner(s):
Instructions:
Dr. M. Woods
Answer four questions only.
Show all working.
Max marks : 100
The acceleration due to gravity g = 9.81 ms-2
Duration:
2 Hours
Sitting:
Autumn 2010
Requirements for this examination:
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you
have received the correct examination paper.
If in doubt please contact an Invigilator.
Q1. (a) Sketch flow pattern and velocity profile diagrams for (i) laminar flow (ii) turbulent
flow.
(8 marks)
(b) State the conditions for laminar flow and turbulent flow.
(6 marks)
(c) Oil of density 800 kgm-3 and viscosity 0.11 Nsm-3 flows with a velocity of 15.0 ms-1
in a pipe of diameter 30 cm.
(i)
State Reynold’s Number equation.
(ii)
Determine Reynold’s number for the flow.
(iii)
State the ranges of Reynold’s number for laminar and turbulent flow. Hence
determine whether the above flow is laminar or turbulent.
Q2. (a) Sketch a labeled diagram of a Venturi tube differential pressure flow meter.
(11 marks)
(6 marks)
(b) A Venturi tube of minimum cross-sectional area 0.30 m2 measures the flow rate of
water in a pipeline of cross-sectional area 0.75 m2. The velocity of flow through the
Venturi meter is 12.0 ms-1.
(i) Determine the volume flow rate (Fv) through the pipe;
(ii) State the Continuity Equation and hence determine the velocity of flow through the pipe.
(12 marks)
(c) What is meant by the term ‘Head Loss’ for a differential pressure flow meter? State
typical percentage values for (i) a Venturi tube flow meter; (ii) an orifice plate flow
meter.
(7 marks)
Q3. (a) Sketch a labeled diagram of a diaphragm box level measurement instrument. Explain
how it measures level.
(9 marks)
(b) A cylindrical tank contains ethanol of density = 790 kg m . The tank is mounted with
-3
its circular base on the ground. The tank has a base radius of 1.60 m and a height of
12.0 m. A diaphragm box level meter is mounted at the base of the tank. (g = 9.81 ms-2)
(i) What is the volume of the tank when it is full?
(ii) What depth is the liquid when a pressure of 27.1 kPa is exerted on the diaphragm?
(iii) What mass of liquid is in the tank when it is 60% full?
(16 marks)
Q4 (a) (i) Sketch a labelled diagram showing the construction of a suitable base metal
thermocouple measuring the temperature of a process at 500oC when the ambient
suitable instrument to measure the signal produced by the thermocouple.
(ii) State the Seebeck Effect to explain the operation of thermocouples.
(10 marks)
(b) State the ‘Law of Intermediate Metals’ for thermocouples. Draw a labelled diagram to
show how this law is used in the practical application of a thermocouple.
(7 marks)
(c) When a Constant Volume Gas Thermometer is at 127oC, its gas is at a pressure of
2.0 x 105 Pa. What is the gas pressure when the temperature is 377 OC ?
Q5 (a) (i)
(8 marks)
Sketch a fully-labelled diagram of a Helical Bourdon Gauge.
(ii) Describe the TWO methods of signal magnification incorporated into the design
of a C-type Bourdon Gauge to magnify the deflection of the Bourdon tube.
(iii) What modification to the design of a C-type Bourdon gauge is used to protect it?
from vibrations?
(iv) Most Bourdon gauges make ‘gauge pressure measurements’. What is meant by
the term ‘gauge pressure measurement’?
(15 marks)
(b) A pressure gauge operates from –50 kPa to 500 kPa. There are 55 intervals on the scale.
Determine for the gauge:
(i)
the span;
(ii) the resolution;
(10 marks)