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DESIGN AND CONSTRUCTION OF LABORATORY SPEED MEASURING TRANSDUCER
There have been significant development in the field of measurement and instrumentation in recent times. Now, it encompasses almost all the areas of science and Technology. Even in our day-to-day life, instrumentation is indispensable.
An automobile driver needs on instrument panel to facilitate him in driving the vehicle properly.
A speed measuring transducer is a device which measures the speed of a rotating shaft or object in revolution per second. This project entails how the speed of a rotating device (Electric Motor) can be measured in the laboratory in other to improve the teaching and learning of the course instrumentation and measurement.
TABLE OF CONTENTS
Title page i
Table of Content vi
1.1 Introduction 1
1.2 General Background of the Project 2
1.3 System Configuration 3
1.4 Transducer 4
1.5 Electrical Transducer 5
1.6 Classification 6
1.7 Basic Requirement of a Transducer 7
1.8 Input-Output Devices and Displays 8
1.9 Basic Characteristic of Measuring Devices 9
1.10 Relevance of the Project 9
CHAPTER TWO: LITERATURE REVIEW 12
2.1 Electronic Speedometer 15
2.2 Centrifugal Force 17
2.3 Mechanical Speedometer 18
2.4 Quartz Electric Speedometer 18
2.5 Inductor Speedometer 18
2.6 Transducers 21
Statement of Problem/Design Problem 22
Method of Solution (Design Procedure) 23
4.1 Smoothing Capacitor 25
4.2 Power Supply Amplifier Unit 26
4.3 The Amplifier Stage 30
4.4 Heat Sink Fundamental 41
4.5 The Display Stage 45
CHAPTER FIVE: Discussion of Results
5.1 Result Achieved 49
5.2 Conversion from Revolution per seconds to Kilometer
per hour 50
6.1 Limitations 52
6.2 Suggestions for Future works 52
6.3 Conclusion 52
6.4 Recommendation 53
The art of measurement is a wide discipline in both engineering and science, encompassing the areas of detection, acquisition, control and analysis of data. It involves the precise measurement and recording of a physical, chemical, mechanical, electrical or an optical parameter and plays a vital role in every branch of scientific research and industrial processes interacting basically with control systems, process instrumentation, and data reduction.
Recent advances in electronics, physics, material sciences, and other branches of science and technology have resulted in the development of many sophisticated and high precision measuring devices and systems, catering to varied measurement problems in such disciplines as aeronautics, science and technology, space, medicine, oceanography and industry in general.
Measurement provides us with a means of describing natural phenomena in quantitative terms. As a fundamental principle of science, Lord Kelvin stated “when you can measure what you are speaking about and express them in numbers, you know something about it and when you cannot measure, it or where you cannot express in number; your knowledge is of a meager and unsatisfactory kind. It may be the beginning of knowledge but you have scarcely in you thought advanced to the stage of science”. In order to make constructive use of the quantitative information obtained from the experiment conducted, there must be a means of measuring and controlling the relevant properties precisely. The reliability of control is directly related to the reliability of measurement. This means that the control and regulation of industrial systems and process depend on accurate measurement. It would not be going too far to state that a variable must be measured accurately to be controlled.
1.2 General Background of the Project
Before the advent of speedometer (speed measuring transducer), people embarked on long journeys, without necessary consideration on the speed at which they move, to cover the required distance needed. Scientist and Engineers have mastered the measurements of distance, from fractions of a millimeter to thousands of kilometers and they can measure time with same degree of accuracy.
A combination of the two gives us a further important measurement called speed. Speed is the distance traveled by an object in a certain time. Measurement of speed, are given by the device named according to the vehicle, in which they are found.
As technology advances, there is a need for a device to measure the speed covered by travelers making use of vehicles and speed of any rotating shaft in science and engineering. A device known as speedometer does this measurement. Now, motor cars have varies electrically operated indicating instruments on the dashboard or instrument panel. These indicating devices range from the temperature indicator, fuel indicator, oil pressure indicator to the speed indicator. The purpose of having these indicating devices is to keep the driver informed about the operating conditions of the car.
1.3 System Configuration
A generalized measurement system comprises the following elements, as shown in fig 1.1.
a. The transducer which converts the measured (measured quantity, property or condition) into a usable electric output.
b. The signal conditioner which converts the transducer output into an electrical quantity suitable for control recording and/or display.
c. The display or readout devices which display the required information about the measured generally in engineering units.
d. The electrical power supply which provides the required excitation to the transducer and the necessary electrical power to the signal conditioners and display devices.
Fig. 1.1: A generalized measurement system
A transducer is defined as a device capable of being actuated by an energizing input from one or more transmission media, and in turn, generating a related signal to one or more transmission systems or media. It provides a usable output in response to a specific input measured which may be a physical or mechanical quantity, property or condition. Actually, the energy in one form of information, transmission system or physical state is transferred to that of another system or state. The responding device may be mechanical, electrical, magnetic, optical, chemical, acoustic thermal, nuclear, or a combination of any two or more of these.
Automation in motion control application is only possible if the controller section receives information about conditions in the manufacturing or scientific process. There conditions include displacement, position, speed, and acceleration. The devices capable of monitoring these conditions are called transducers. The transducer performs the measurement of the condition and produces a feedback that provides information on the result. Some transducers produce an analog output signal while other produces a digital output signal.
1.5 Electrical Transducer
An electrical transducer is a sensing device by which a physical, mechanical, or optimal quantity to be measured is transformed directly, with a suitable mechanism, into an electrical voltage or current proportional o the input measured. The input versus output energy relationship takes a definite reproductive function. The output to and the output to time behaviour is predictable to a known degree of accuracy, sensitivity and response, within the specified environmental conditions. The significant parameters which dictate the transducer capability are linearly, repeatability, resolution, and reliability.
The main advances of an electrical transducer may be summarized as follows:
a. The electrical output can be amplified to any desired level.
b. The output can be indicated and recorded remotely at a distance from the sensing medium. Further, more than one indicator can be actuated simultaneously.
c. The output can be modified to meet the requirements of the indicating or controlling equipment. The signal magnitude can be related in terms of the voltage or current. The analog signal information can be converted into a digital format for display, print-out or on-line computation.
Since the output can be modified, modulated, or amplified at will, output signal can be easily adapted for recording on any suitable multichannel recording oscillograph which can cater to a number of electrical transducers simultaneously.
d. The signals can be conditioned or mixed to obtain any combination with outputs of similar transducers or control signals as in an air data computer or adaptive control systems. A typical example is the Mach number measurement with two measurands.
e. The size and shape of the transducer can be suitably designed to achieve the optimum weight and volume.
f. The contour design and dimensions can be so chosen as not to disturb the measured phenomena, as in the case of turbulence measurements. In certain cases the size can be made extremely small, thereby increasing the natural frequency to a high value. An example is the miniature piezoelectric pick-up employed for vibration measurements.
All electrical transducers are broadly classified under two categories, viz, active and passive transducers. Active transducers are self-generating devices, operating under energy conversion principles. They generate an equivalent electrical output signal, e.g. from pressure to charge or from temperature to electrical potential, without any external energizing source. Passive transducers operate under energy controlling principles. They depend upon the change in the electrical parameter (resistance, inductance or capacitance) whose excitation or operation requires secondary electrical energy from an external source. A typical example is the case of the strain gauge excited by a dc voltage source or differential transformer energized by a carrier wave signal.
1.7 Basic Requirement of a Transducer
A transducer is normally designed to sense a specific measurand or to respond only a particular measured. A complete knowledge of the electrical and mechanical characteristic of the transducer is great importance while choosing a transducer for a particular application. Often, it is deemed essential to get details of these characteristics during the selection of instrument for the experiment concerned. The basic requirements are:
a. Ruggedness: Ability to withstand overloads, with safety stops for overload protection.
b. Linearity: Ability to reproduce input-output characteristics symmetrically and linearly.
c. Repeatability: Ability to reproduce the output signal exactly when the same measurand is applied repeatedly under same environmental conditions.
d. Convenient instrumentation: Sufficiently high analog signal with high signal to noise ratio; digital output preferred in many cases.
e. High stability and reliability: Minimum error in measurement, unaffected by temperature, vibration and other environmental variations.
f. Good dynamic response: Output is faithful to input when taken as a function of time. The effect is analyzed as the frequency response.
g. Excellent mechanical characteristics that can affect the performance in static, quasi-static, and dynamic states.
1.8 Input-Output Devices and Displays
All instrumentation systems have to process either a display that a human operator can real out from and interpret, or an output device that enables the transfer of information from the instrumentation system to a general purpose or dedicated computer. Input – Output device are of various forms depending on such factors as speed, (i) types of record required, and type of system to which data is fed (ii) the type of data via analog or digital.
An analogue output display is adapted for this project because it can theoretically display an infinite number of speeds, accuracy, it can be clearly seen in the strong sunlight or other bright light and also it does not take away sense of change in speed. Analogue output display is adequate for the design.
1.9 Basic Characteristic of Measuring Devices
The function of a measuring device is to sense or detect a parameter encounter in an industrial process or in scientific research, such as pressure, temperature, on, resistance, voltage, current, and power.
The measuring device must be capable of faithfully and accurately deterring any changes that occur in the measured parameter. For control purposes, the measuring instrument either generates a warning signal to indicate the need for a manual change or activates a central device automatically.
1.10 Relevance of the Project
A speed measuring transducer (speedometer) design and construction is targeted at providing one of the major experiments in the control or measurement and instrumentation laboratory.
It is also aim at measuring the speed of electric motor and motor vehicles with an analog read out or display because of the limitations in digital speedometer. For example, while an analog speedometer can theoretically display an infinite number of speeds, a digital speedometer can only display speeds in whole numbers.
Other limitations of digital speedometer includes
· They took away the sense of change in speed that provided by an analog speedometer.
· They were hard to see in the strong sunlight or other bright light.
· They were expensive to repair in the event of malfunction.
As a result of these issues, digital instrument panels were phased out of vehicles throughout the 1990s. And have been replaced with traditional analog gauges in most vehicles, including those from luxury divisions.
The design and construction of a speed measuring transducer is aimed at laboratory display of how a speedometer and other speed measuring devices work.
The project design involves four stages as designated in the block diagram shown in fig 1.1
The measured parameter is the rotating device whose speed is to be measured. With the aid of a pulley, the mechanical rotation is transferred into the rotation of the motor of a dynamo which produces electrical impulse. The impulse generated is then amplified by a well designed amplifier circuit whose output is being display by a speed dial calibrated to read in revolution per minutes.
ORGANISATION OF THE REPORT
The write up comprises
· Chapter one is the introductory chapter and made up of the background information, the purpose and scope of the work.
· Chapter two is the literature review, review existing, types of speedometer. The reviews are there to establish relevant knowledge in the subject matter under consideration.
· Chapter three contains the problems statement of design problem.
· Chapter four contains the method of solution. It discusses how the problem stated in chapter three is solved.
· Chapter five gives the results
· Chapter six this contains suggestions for future works and conclusion, limitation and recommendations.
· References indicate the sources of information used in the write-ups.