real world measurements

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Real world measurements. (not ModCon II there will be no modeling or control). Measuring things. M aking accurate measurements is an essential part of all branches science and engineering. - PowerPoint PPT Presentation


A new semester

Real world measurements(not ModCon II there will be no modeling or control)1Measuring thingsMaking accurate measurements is an essential part of all branches science and engineering. Much (all?)of our understanding of the world was born from experimental measurements (often ones that disagreed with the current theory).Models of systems are useless without validation. Performance of engineered systems must always be measured and tested.

Experiment is the sole judge of scientific truth Feynman2


Modern engineering systems

Physics classical and today

Michelson-Morley 1887

Large hadron collider

2011And corporations want to instrument your life (this is a conspiracy)

What you will learn (hopefully)Make a set of physical measurements. Analyze and present experiment data. Conduct basic error analysis of data. Design a basic computer based experimental system. Use measurements test physical models.

This class is just the beginning

8LeverageElectronics keep getting cheaper. Wireless keeps getting cheaper and better.Sensors getting smaller. GPS is getting easy and cheap.IPhone and Wii are driving down complex sensor costs.Ability to interface to computers keeps getting easier.PCBs are fast and cheap. 9Course structure (some details TBD)Week 1Individual Lab: Intro to data acquisition - accelerationWeek 2Individual Lab: EKGWeek 3Individual Lab: Mechanical Stress/strainWeek 4Individual Lab: Signal processingWeek 5Individual Lab: Pulse OximeterWeek 6Individual Lab: Mechanical vibrationsWeek 7 Individual Lab: TBDWeek 8Team Project Week 9Team Project Week 10Team Project Week 11Team ProjectWeek 12Team ProjectWeek 13Team ProjectSpring break10Project theme The natural worldEnvironment Weather balloonsLakes, rivers.Weather, wind, rain.Bio-instrumentationEEGPulse oximeterBiomechanics (accelerometers)

Possible examples:Projects can focus on building a reasonably challenging sensor/circuit or using commercial sensors and focus on the experiment and the data.

A few things.This is not an EE course.Ninjas.Lab reports focus mainly on results. Weekly labs will be individual, we will try to minimize the sharing of equipment. Team project will be in groups of about 4. Significant changes in labs from last years class.

12Grades yes we have to give themStorey conjecture: If you turn everything in on time, come to class, spend a reasonable amount of time on homework, and put forth a reasonable effort, the lowest grade you will receive is a B. Corollary: You can easily get a C, D, or F by not doing the above mentioned tasks. 13So lets get down to businessHardware USB data acquisition

Analog to digital conversion

What is the sample rate?Our system has a 14 bit ADC, if we set the range to 10 V, what is resolution?Resolution14 bit ADC: 00101011101101214=16384 numbersResolution = range/16384

Eg: range is +10 to -10 V; 20/16384=1.2 mVrange is +1 to -1 V; 2/16382 = 0.12 mVAliasing error


What are sources of noise?Types of noiseThermal (Johnson) noise due to thermal motion of electronsShot noise discrete nature of electrons1/f noise or flicker noise

InterferenceElectromagnetic interference (man-made or natural)Cross-talk coupling between different signal lines

How accurate is the DAQ?If we measure 1 V, should we believe it?Test itSimple voltage divider demoWhats this voltage?

==5VRRUSB 6009 input impedance

==5VRRii is not 0!Analog output demo

==1VR=10K and 100 Source impedance

DAQ Analog Output=1V=100 What is R source for our DAQ?Generic sensor measurementSensorMeasurement- DAQ

If R source is small, and Rmeas is big, then you measure VsensorOtherwise, you might be measuring something else!26This week: Accelerometers

27Matlab data acquisition toolboxIn class exercisesSee Data Acq. Toolbox tutorial, try exercises 1, 2, and 3. Work with the person next to you.


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