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Unformatted text preview: CHAPTER 1 INTRODUCTION ME 365 is the first course in a three course sequence in the undergraduate curriculum, designed to acquaint you with systems, measurements and control. The other courses are ME 375 and ME 475. ME 365 is devoted to measurement systems, and covers the basic principles of the art of making good measurements. At the end of the course you should have a reasonable grasp on what you need to look for when putting a measurement system together, and how to calibrate the system to make sure that it meets all of your (and your boss's) specifications. In this course you will only make some fairly simple mechanical measurements of temperature and motion, primarily displacement. However, the basic principles that you learn will have relevance to all measurements that you are likely to make. In making measurements of mechanical systems you will be taking some mechanical quantity, e.g., temperature, displacement, or flow rate, and creating a voltage that is proportional to it. Hopefully in doing so you will not change the process whose response you are trying to measure. This voltage can then be measured with a voltmeter, a digital multimeter, an oscilloscope or a computer equipped with analog to digital conversion boards. As such, you will be dealing with electrical circuits, even though you are actually interested in mechanical phenomena. Some Mechanical Engineering students feel uncomfortable with this; after all did you not choose ME in preference to EE? However, lets think about mechanical systems we are familiar with, e.g., automobiles, machines that most ME's are very interested in. Open up the hood, there we see both electrical and mechanical systems working together. Learning about how to make measurements of mechanical phenomena will be your first step in learning about electro-mechanical systems. Why Take Measurements? First let’s try to answer the question, why do you, as a mechanical engineer, need to understand the basics of measurements? I am assuming that as a mechanical engineer you are interested in studying mechanical systems. You want to be able to design better machines, fix machines that don't work, and not design machines that have catastrophic failures resulting in injury or death. You must therefore have tools available to you to help you do this. An ability to take measurements is one of these tools. When we are interested in the behavior of a machine or its component parts, we use our understanding of the physics that governs the behavior of the components, make some assumptions, and then derive a set of governing equations. Simulating or solving these equations allows us to examine how parameters, e.g. material properties, affect the nature of the response of the machine. In machine design, we can use our knowledge of the conditions under which the 1-2 machines will operate and the desired response to guide our choice of the material properties. We use the models to optimize our parameter choices....
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- Fall '07