Lecture 1 (Basic Concepts of Measurement Methods).pptx

vvvvxccccccccccccccccccc

1. Measurement and Instrumentation (ME-331) Instructor: Dr. Waqar Ahmed Mechanical Engineering Department University of Engineering & Technology, Taxila [email protected]

2. Learning Outcomes Identify the major components of a general measurement system, and state the function of each Develop an experimental test plan Distinguish between random and systematic errors Describe and define the various error types Define a standard and distinguish among primary, secondary, and transfer standards Clearly delineate defined and derived dimensions in various unit systems. Dr. Waqar Ahmed, MED, UET Taxila 2

3. 1.1 Introduction Measurement: “An act of assigning a specific value to a physical variable” Measured Variable: “The physical variable above is a measured variable” Measurement System: “A tool used for quantifying the measured Variable” Why do we need to measure? Dr. Waqar Ahmed, MED, UET Taxila 3

4. 1.2 General Measurement System Dr. Waqar Ahmed, MED, UET Taxila 4 Difference in sensor and transducer?

5. 1.3 Experimental Test Plan Purpose of an Experimental Test: “To answer a question” Example: Mileage of your car (Mileage = Distance / Fuel) Steps Parameter Design plan: Identify the objective and variables / parameters System and Tolerance Design Plan: Select measurement technique, equipment, test procedure Data Reduction Design Plan: Plan to analyze, present, interpret and use the experimental data Dr. Waqar Ahmed, MED, UET Taxila 5

6. Variables Independent Variables Dependent Variables Extraneous Variables Continuous extraneous variables Discrete extraneous variables Control of Variables Control Parameters Noise and Interference Dr. Waqar Ahmed, MED, UET Taxila 6

7. Random Tests Dr. Waqar Ahmed, MED, UET Taxila 7 Example of car mileage for randomization

8. Dr. Waqar Ahmed, MED, UET Taxila 8   Power Source Voltmeter Find independent , dependent and extraneous variables   Gas obeys ideal gas law C is parameter   Example 1.1 Pressure Transducer   V   Room Temperature   I  

9. Randomization of Example 1.1 (Ex 1.2) Develop a test matrix that will minimize the interference effects of any extraneous variables Our strategy: Change volume, control gas temperature and measure pressure We must avoid false trends in the measurement of pressure To minimize the effects of we will have to randomize the changing values of volumes Let us suppose we set 7 different volumes in descending order ( ) and read respective pressure values We may randomize the values like in the given sequence instead of ascending order:   Dr. Waqar Ahmed, MED, UET Taxila 9

10. Another Example A, B, C are material types in an experiment are three different operators doing tests are the temperatures at which tests are to be performed How do you plan to minimize the effects of extraneous variable of operators?   Dr. Waqar Ahmed, MED, UET Taxila 10

11. Replication and Repetition What is Replication? What is Repetition? What is the advantage of both? What do they signify? Dr. Waqar Ahmed, MED, UET Taxila 11

12. Concomitant Methods Obtain two or more estimates Use a different method for each estimate This approach increases the trust in measurement Present and discuss few examples How can you measure volume of this cylinder? How can you be sure of your measurement? Dr. Waqar Ahmed, MED, UET Taxila 12 L    

13. 1.4 Calibration Static Calibration Static Sensitivity Dynamic Calibration Range Discuss examples of calibration Dr. Waqar Ahmed, MED, UET Taxila 13

14. Conclusion Rest of the chapter is reading assignment of class After reviewing the whole chapter every student has to solve one problem each from the problems at the end of Chapter 1 Sequence of problems assignment: Roll # 1 => Q # 1.1 and so on When questions finish, the repetition will start Assignment does not have to be submitted Dr. Waqar Ahmed, MED, UET Taxila 14