A Project Report for Instrumentation and Measurements - Coursework Example

Design ReportDesign Report Template Project name Instrumentation and Measurement ENM2104 Engineering Design Process Confidentiality Notice Access to this document and referenced documents is provided to the recipient under the following conditions: 1) The contents are to be used solely for the purposes of the ENM2104 Unit at The School of Engineering, Edith Cowan University 2) The document will not be made accessible to any external party other than (if necessary) lecturers currently engaged by ECU under a contract which addresses confidentiality 3) Any requirement to vary these conditions is to be referred to the ENM2104 Unit Coordinator © Edith Cowan University 2015 Except as provided by the Copyright Act 1968, no part of this document may be reproduced, stored in a retrieval system or transmitted in any form or by any means without the prior written permission of the Edith Cowan University. Enquiries should be directed to the ENM2104 Unit Coordinator. Executive Summary (Max 100 words) The project is about force measurements using a strain gauge as the sensor. The main components of the experiment include the primary sensing element, the strain gauge, the data conversion unit (In this case is the Wheatstone bridge), data manipulation performed by the amplifier and data logger as well as the presentation unit which is in form of a printout of the force measurements due to varying loading on the test piece. Background (Max 50 words) A strain gauge is a primary sensory device whose resistance changes when stretched or compressed. When used as a primary sensing element, the change in resistance is converted into a more suitable data signal form. The output can be manipulated such that change in resistance gets expressed as a function of the parameter being measured. For the project under consideration, the output was shown as a function of force by use of the data logger. Scope (Max 50 words) The project entails designing of a force measuring system by use of the most effective sensors. The project makes use of various components apart from the sensors. The project should be affordable and should be rugged enough to sustain loadings under consideration. The design of the projects would be met within the datelines provided by the respective co-ordinators. Design Summary (Max 50 words) The measurement system consists of primary sensory element, data conversion unit, manipulation unit, transmission unit, presentation and storage unit. The software incorporated into the system is essential in the data acquisition process, conversion and manipulation as it oversees all the functions of related hardware ensuring they are well executed. Software entails the recording analysis and control unit in within the system Unresolved Items (Optional) TABLE OF CONTENTS 1.Introduction (Max 100 words) 7 1.1. Description of the Project (Max 100 words) 7 Advantages of the strain gauge 9 2.Implementation (Total Max 300 words) 12 2.1. Abstracting the Problem 12 The primary concern in this project was to record slight changes in forces caused by variation of the load weights that were of different sizes. It thus, called for the use of a very highly accurate sensor that had better off static, dynamic characteristics that would not bring errors in data collection if any gets encountered. A variety of sensors were available but considering the mentioned factors it was evident that a strain gauge was the most appropriate sensor required. 12 Division of Tasks 12 2.2. Problems Faced 13 3.Sensor Selection (Total Max 300 words) 13 3.1. Identification of the Sensor Type 13 3.2. Performance Test of the Sensor 14 4.Measurement System Implementation (Total Max 300 words) 15 4.1. Hardware Configuration 15 4.2. Software Configuration 15 The software configuration entails the set of instructions and procedures that control the data acquisition unit. It consists of the data recording unit package allowing exporting of data into a spreadsheet, the analysis software that manipulates the recorded data signal and control software that oversees whole process 16 5.Conclusion (Max 100 words) 16 A strain gauge is one of the most efficient sensors for measurement of force and displacement. Such a result gets attributed to the high level of accuracy precision linearity, reproducibility and reliability. It also useful in small measures determination compared to other measurement sensors. Its versatility makes it most efficient and economical for use as a single sensor can be used to measure force pressure and also displacement depending on the way it has been connected. During the experiment, some errors may have been encountered that include inaccuracy in recording of data, manipulation or faulty equipment. It could result in inaccurate data from what was expected. 16 6.Appendices 17 1. Introduction (Max 100 words) Measurement is the method of getting some data about a given aspect of a particular environment. Measurements may be descriptive, objective or subjective. There are two basic methods of measurements. One is by direct comparison where measurand gets compared to a standard value or indirect comparison where a measurand gets converted to a form that it's expressed as a function of the input. Some of the measurement forms include counting sorting and ordering. Various types of scales are used which include ratio absolute and order scales. Instruments can get classified as either passive or active depending on how they interact with the environment. A sensor is an energy conversion unit from one to a different form for purposes of measurements .sensors have different static and dynamic characteristics which whose details gets discussed later in the report. Basic steps of analysis are sensing of the parameter the translation manipulation transmission ,backup and display of the data. Sensors can get classified as mechanical chemical or electrical sensors. In the project under consideration, a mechanical sensor would be put into use. Mechanical sensors are the most suitable compared to others. 1.1. Description of the Project (Max 100 words) The project's focus will be on the use of a mechanical sensor to measure forces caused by an increase in loads. The changes in the forces are small changes, therefore, a very accurate method of measurement is required. Considering factors causing disturbance to the system, minimum levels of data values to be measured and null measurements, I opted to use a strain gauge to carry out the measurement of force. Where during loading of the test piece, strain gauge defects, and the signal sent to Wheatstone bridge where it gets converted into voltage signals. The signals are further amplified by the amplifier and manipulated by the data logger as a function of force that finally gets displayed to the user. Equipment’s required during the experiment a) Two strain gauges- A b) Connecting cables-D c) An amplifier-F d) Data logger -F e) Wheatstone bridge.-E f) Test piece-B G) Weight -C Experimental layout Procedure a) Cleaning of the test piece and taking dimensions of its length width and thickness b) Attachment of the strain gauge to the test piece using superglue c) Fixing of the test piece to the test bench d) Connection of the strain gauge to Wheatstone bridge using cables e) Connection from the Wheatstone bridge to amplifier then finally to the data logger using the connection cables f) Loading of varying weights from 50 grams and noting taking the printout from the data logger Input measurands Force is a push or a pull acting on a given body or surface caused by an external element. During the experiment, weights in range of 0-1000 grams were used to give a force range measurement of 0-10 N . It was considered as a standard for experimental purposes. Input sensor A strain gauge was the preferred choice of the sensors available at our disposal. When a loading is applied on the test piece, it deflects by an absolute value which is detected by the strain gauge attached to it. The deflection gets transmitted to the Wheatstone bridge for conversion to voltage signals before further conversion by the data logger. Advantages of the strain gauge i) Good accuracy :output values are close to the correct values ii) Good reproducibility; it easily can generate same values if the working conditions are maintained constant iii) Good linearity: change in output signal is proportional to change in input signal iv) Good sensitivity to measured parameter changes Disadvantage of a strain gauge i) Main is not appropriate for measurement of large forces mostly accurate when dealing with small amounts of forces With some of the advantages mentioned above it's evident that the data acquired from such an experiment is reliable and precise as the small amount of effects are to be measured. Input signal deflection is in an analogue form that will be converted to a digital form voltage signal by the Wheatstone bridge before its amplification and manipulation by the amplifier and data logger respectively. Analogue to digital signal conversion In our experiment a deflection type Wheatstone bridge was use as shown above. Main function was to produce an output voltage that changes as the input variable changes. The governing equation is Where V0- output voltage Vi- induced voltage Ru - unknown resistance R1, R2, R3 are known resistance one two three respectively The three main steps in analogue to digital signal conversion are i) sampling :conversion of continuous signals into a series of discrete intervals ii) Quantification: discrete component converted to a given finite value ii) encoding of the signal :amplitude signals are translated into digital value code Signal amplification After the conversion of the signal to digital signal, it’s amplified with help of an operational amplifier. It consists of two terminals; the inverting and non-inverting terminal. The unprocessed signal is linked to the inverting terminal while the other connected to the ground as shown in the circuit diagram below. In ideal conditions the processed signal VO is given by the equation Ratio between the R1 and R2 defines the amplification of the signal Actuator element Found within the data logger whose primary function is to convert the digital signals back to analogue signals for output purposes. Composed of a resistive ladder at the entry of an operational amplifier as illustrated below for an 8-bit data signal. If binary value is 1 the switch is complete else if a value of 0 is provided its open for the above illustration the input to the actuator is given by equation Whereas the output value given as Data acquisition In the acquisition process, and SCX1 1122 was selected to obtain all the 8 bits signal inputs from the sensory element. It had the following features a) Optimum scanning rate of 100S/s b) Voltage Excitation at 3.3333 volts c) A key in range of +5 or -5 After filtering and sorting of the signals, they get converted back to a single plug-in data acquisition board. The acquisition system provides an efficient sampling rate of about 6S/s which is good and signals mat not require filtering or sorting at such a rate due to minimum interference in their quality. The acquisition used was an efficient mode. Data acquisition software It has several functions in a data acquisition system that includes: presentation reviewing, external transfer of signal and analysis of data signals. Waveform recording software specifically Win Daq/Xl type was used as it quickly allowed display data in a tabular form such as Excel. Analysis software a win Daq form browser software was selected it reviews the files initially recorded by the win Daq software. Control software package X: controls instrument pack got chosen as it gives a more real virtual area when it comes to manipulation of recorded signal Block diagram summarizing functions of a control software 2. Implementation (Total Max 300 words) 2.1. Abstracting the Problem The primary concern in this project was to record slight changes in forces caused by variation of the load weights that were of different sizes. It thus, called for the use of a very highly accurate sensor that had better off static, dynamic characteristics that would not bring errors in data collection if any gets encountered. A variety of sensors were available but considering the mentioned factors it was evident that a strain gauge was the most appropriate sensor required. Division of Tasks For a more comprehensive measurement, the measurement system was divided into various stages that included Primary sensing element: strain gauge whose function was to measure the physical parameter strain due to application of some loading on the test piece Data conversion element: Wheatstone bridge that converted the strain from the pressure gauge into induced voltage for easier manipulation Data amplification factor : amplification by the amplifier that catered for loss on the signal during transmission. Data manipulation: The data logger also had an important part of the data manipulation as it converts amplified voltage signal into a function of force that later gets displayed as output Data transmission: responsible for the movement of signals between various elements of the measurement system this were electrical cables in the experiment. Data presentation: printout produced by the data logger that enables the user to see the trend in change of force due to application varying weights. Data storage: a secondary memory can be used to store the data for future use. 2.2. Problems Faced Some of the challenges encountered included were: errors during the application of the loads this was caused by inaccuracy in gently loading of the system to produce accurate results. A faulty data logger that is essential to the manipulation of the signals as the printout of the signal was not that clear. 3. Sensor Selection (Total Max 300 words) 3.1. Identification of the Sensor Type To identify the most appropriate sensor four main things were considered Static and Dynamics characteristics required For static characteristics’ accuracy, hysteresis, linearity, range, span, resolution and sensitivity of the instruments were the top priorities. Taking into the account of dynamic characteristics’ of the instruments available such as speed to respond to change in force the drift and lag were primary considering factors. Putting this in the account and the fact that force measurement required was the minimal amount we opted for a trains gauge compared to other instruments that could also measure force. Extent of disturbance expected During operation with a variation of 50 grams weights, very small movements are expected of the test piece this needed a sensor of high accuracy precision and low range to get required results hence selection of a strain gauge over other sensors Durability maintenance and operation cost A durable easy to maintain and operate sensor got required for efficiency purposes this made opt for use of a strain gauge this was because it had advantages such as one once the whole system had been set up the experiment was easy to carry out as it only required on to change the loading and the data logger produces the data in a printout form . Maintenance of the system was considerably cheap as it entailed careful keeping of the Wheatstone bridge amplifier cables and strain gauge when they were not in use. Environmental conditions under which the instrument is to be used. Since the data signal got carried in the workshop there were very minimum effects from atmospheric conditions that could interfere with accuracy of the data being measured hence we had no problem with still maintaining a strain gauge as our sensory element in the measurement system. 3.2. Performance Test of the Sensor Calibration is a process that is periodically done to ensure that the closeness to the actual value of data and relation between input and output of the strain gauge during measurements are reliable. There are two ways of calibration direct or indirect method. In our case, we used the indirect method to calibrate the strain gauge. Shunt calibration procedure was implemented to get a measurement of the output signal from a predetermined input signal. Procedure Output voltage is always equal to the potential difference between the points A and B and there equation is given by Since eo= EA-EB Then The equation allow determining of output voltage by reducing the resistance in the shunting process. For example lowering R1/R2 by R1 in shunting procedure lead to negative change in output in shunting process. Sources of errors during calibration process a) Determination of the proper shunt resistance b) Errors due to non-linearity of Wheatstone bridge. 4. Measurement System Implementation (Total Max 300 words) 4.1. Hardware Configuration A block diagram showing process flow of the measurement of the various hardware components Strain gauge: this is the primary sensing element that is attached to one end of the loaded beam its deflection due to application of force gets transmitted to the Wheatstone bridge by transmission cables Wheatstone bridge is the data conversion element that transforms the data from deflection into induced voltage that gets then sent to the amplifier. Amplifier increases the magnitude of the converted input data by a given ration ensuring that losses encountered during transmission do not affect the final required quantity of output data Data logger : converts amplified voltage data back to deflection and expresses it further as a function of force which is the displayed in form of a print out or send to the backup unit for storage that may be necessary for future reference. 4.2. Software Configuration The software configuration entails the set of instructions and procedures that control the data acquisition unit. It consists of the data recording unit package allowing exporting of data into a spreadsheet, the analysis software that manipulates the recorded data signal and control software that oversees whole process 5. Conclusion (Max 100 words) A strain gauge is one of the most efficient sensors for measurement of force and displacement. Such a result gets attributed to the high level of accuracy precision linearity, reproducibility and reliability. It also useful in small measures determination compared to other measurement sensors. Its versatility makes it most efficient and economical for use as a single sensor can be used to measure force pressure and also displacement depending on the way it has been connected. During the experiment, some errors may have been encountered that include inaccuracy in recording of data, manipulation or faulty equipment. It could result in inaccurate data from what was expected. 6. Appendices Appendix 1 Resistive ladder representation Appendix 2 Analogue to digital conversion diagram Appendix 3 Connection of the Wheatstone’s bridge Read More

Considering factors causing disturbance to the system, minimum levels of data values to be measured and null measurements, I opted to use a strain gauge to carry out the measurement of force. Where during loading of the test piece, strain gauge defects, and the signal sent to Wheatstone bridge where it gets converted into voltage signals. The signals are further amplified by the amplifier and manipulated by the data logger as a function of force that finally gets displayed to the user. Equipment’s required during the experiment a) Two strain gauges- A b) Connecting cables-D c) An amplifier-F d) Data logger -F e) Wheatstone bridge.-E f) Test piece-B G) Weight -C Experimental layout Procedure a) Cleaning of the test piece and taking dimensions of its length width and thickness b) Attachment of the strain gauge to the test piece using superglue c) Fixing of the test piece to the test bench d) Connection of the strain gauge to Wheatstone bridge using cables e) Connection from the Wheatstone bridge to amplifier then finally to the data logger using the connection cables f) Loading of varying weights from 50 grams and noting taking the printout from the data logger Input measurands Force is a push or a pull acting on a given body or surface caused by an external element.

During the experiment, weights in range of 0-1000 grams were used to give a force range measurement of 0-10 N . It was considered as a standard for experimental purposes. Input sensor A strain gauge was the preferred choice of the sensors available at our disposal. When a loading is applied on the test piece, it deflects by an absolute value which is detected by the strain gauge attached to it. The deflection gets transmitted to the Wheatstone bridge for conversion to voltage signals before further conversion by the data logger.

Advantages of the strain gauge i) Good accuracy :output values are close to the correct values ii) Good reproducibility; it easily can generate same values if the working conditions are maintained constant iii) Good linearity: change in output signal is proportional to change in input signal iv) Good sensitivity to measured parameter changes Disadvantage of a strain gauge i) Main is not appropriate for measurement of large forces mostly accurate when dealing with small amounts of forces With some of the advantages mentioned above it's evident that the data acquired from such an experiment is reliable and precise as the small amount of effects are to be measured.

Input signal deflection is in an analogue form that will be converted to a digital form voltage signal by the Wheatstone bridge before its amplification and manipulation by the amplifier and data logger respectively. Analogue to digital signal conversion In our experiment a deflection type Wheatstone bridge was use as shown above. Main function was to produce an output voltage that changes as the input variable changes. The governing equation is Where V0- output voltage Vi- induced voltage Ru - unknown resistance R1, R2, R3 are known resistance one two three respectively The three main steps in analogue to digital signal conversion are i) sampling :conversion of continuous signals into a series of discrete intervals ii) Quantification: discrete component converted to a given finite value ii) encoding of the signal :amplitude signals are translated into digital value code Signal amplification After the conversion of the signal to digital signal, it’s amplified with help of an operational amplifier.

It consists of two terminals; the inverting and non-inverting terminal. The unprocessed signal is linked to the inverting terminal while the other connected to the ground as shown in the circuit diagram below. In ideal conditions the processed signal VO is given by the equation Ratio between the R1 and R2 defines the amplification of the signal Actuator element Found within the data logger whose primary function is to convert the digital signals back to analogue signals for output purposes.

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