L12_ECE4001_Spring_2011

L12_ECE4001_Spring_2011 - Whats the big deal about how good...

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1 Slide #1 ECE 4001 L12 © 2011 Lecture 12 Engineering Measurements – Part 1 Slide #2 ECE 4001 L12 © 2011 How do you know your test measurements are valid? Since NIST traceability actually guarantees little about your test data, how do you know? Could you prove validity to your customer? What is the right measurements solution for your testing requirements? Is it really as simple as the vendors say? What is your real cost of invalid, ambiguous data causing retest or, worst of all, hardware redesign? NIST (National Institute of Standards and Technology) What’s the big deal about how good my measurements are? http://www.aticourses.com/applied_measurement_engineering.htm Slide #3 ECE 4001 L12 © 2011 Measurement Issues To Be Addressed • Elements of a Measurement System • Error and Uncertainty • Instrumentation Errors • Calculating Experimental Errors • Calibration Issues • Experimental Test Plans Slide #4 ECE 4001 L12 © 2011 Elements of a Measurement System • Sensor/transducer – Detect a signal or stimulus (what we are measuring) and produce a measurable output • Signal conditioning – Convert the sensor output into a more usable form • Display/data recorder – Display and/or record the measurement results
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2 Slide #5 ECE 4001 L12 © 2011 Example: Thermometer • Sensor: Liquid in the bulb responds to increase in temperature by expanding • Signal Conditioning: Expanding liquid travels up the small tube so that it can be seen • Display/Recorder: Scale marked on the small tube displays the temperature; manual recording of data Slide #6 ECE 4001 L12 © 2011 Example: Electronic Caliper • Sensor: Mechanical calipers • Signal Conditioning: Encoding device to convert mechanical motion to electronic format • Display/Recorder: Digital readout and manual recording of data Slide #7 ECE 4001 L12 © 2011 Example: Thickness Gage • Sensor: Ultrasonic transducer • Signal Conditioning: Analog signal is digitized and processed to determine the material thickness • Display/Recording: Numerical display and built-in data logger Slide #8 ECE 4001 L12 © 2011 Error and Uncertainty • What is error? • Error vs. uncertainty • Human errors • Systematic errors • Random errors • Accuracy and precision
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3 Slide #9 ECE 4001 L12 © 2011 Experimental Error • Experimental error does not imply that there is any mistake in the measurement process (although there may be) • The experimenter never (or rarely) knows
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This note was uploaded on 04/18/2011 for the course ECE 4001 taught by Professor Frazier during the Spring '09 term at Georgia Tech.

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L12_ECE4001_Spring_2011 - Whats the big deal about how good...

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