Real world measurements

1. Real world measurements (not ModCon IIthere will be no modeling or control)

2. Measuring things • Making 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” Feynman

4. Healthcare

5. Modern engineering systems

6. Physics – classical and today Michelson-Morley 1887 2011 Large hadron collider

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

8. 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

9. Leverage • Electronics 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.

10. Course structure (some details TBD) Spring break

11. Project theme – The natural world Possible examples: • Environment • Weather balloons • Lakes, rivers. • Weather, wind, rain. • Bio-instrumentation • EEG • Pulse oximeter • Biomechanics (accelerometers) Projects can focus on building a reasonably challenging sensor/circuit or using commercial sensors and focus on the experiment and the data.

12. 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.

13. Grades – yes we have to give them • Storey 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.

14. So… let’s get down to business

15. Hardware – USB data acquisition

16. 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?

17. Resolution 14 bit ADC: 00101011101101 214=16384 numbers Resolution = range/16384 Eg: range is +10 to -10 V; 20/16384=1.2 mV range is +1 to -1 V; 2/16382 = 0.12 mV

18. Aliasing error

19. Noise What are sources of noise?

20. Types of noise • Thermal (Johnson) noise – due to thermal motion of electrons • Shot noise – discrete nature of electrons • 1/f noise or flicker noise Interference • Electromagnetic interference – (man-made or natural) • Cross-talk – coupling between different signal lines

21. How accurate is the DAQ? • If we measure 1 V, should we believe it? • Test it

22. Simple voltage divider demo R =5V = R What’s this voltage?

23. USB 6009 – input impedance i R =5V = i is not 0! R

24. Analog output demo R=10K and 100 Ω =1V =

25. Source impedance DAQ Analog Output =100 Ω =1V What is R source for our DAQ?

26. Generic sensor measurement If R source is small, and Rmeas is big, then you measure Vsensor Otherwise, you might be measuring something else! Sensor Measurement- DAQ

27. This week: Accelerometers

28. Matlab data acquisition toolbox

29. In class exercises • See Data Acq. Toolbox tutorial, try exercises 1, 2, and 3. Work with the person next to you.