Sampling Chapter 2 ME 392 30 January 2012 week 4

1. SamplingChapter 2ME 39230 January 2012week 4 Joseph Vignola

2. Assignment 2 Assignment 2 was good I think most people are getting the hang of LabVIEW

3. Assignment 2 Assignment 2 was good I think most people are getting the hang of LabVIEW You where asked to average noisy data Send and receive it through the BNC 2120 box And write it to have file

4. Assignment 3 Assignment 3 is about Matlab acquisition

5. Assignment 3 Assignment 3 is about Matlab acquisition For this one you are being asked to send and receive date through the microphone and headphone jack that are on all modern PCs and Macs. Also you are asked to use Matlab’s handle graphs This assignment requires a little bit of explanation in the write-up

6. Assignment 3 Assignment 3 is about Matlab acquisition The Matlab notes can be found on the class webpage

7. Measuring Some Changing Quantity In a lot of engineering problem we need to measure some quantity that changes over space or time.

8. Measuring Some Changing Quantity In a lot of engineering problem we need to measure some quantity that changes over space or time. Think about how the temperature outside changes

9. Measuring Some Changing Quantity In a lot of engineering problem we need to measure some quantity that changes over space or time. Think about how the temperature outside changes We can think about sampling the temperature every so often and writing it down

10. Measuring Some Changing Quantity In a lot of engineering problem we need to measure some quantity that changes over space or time. Think about how the temperature outside changes We can think about sampling the temperature every so often and writing it down

11. Measuring Some Changing Quantity In a lot of engineering problem we need to measure some quantity that changes over space or time. Think about how the temperature outside changes We can think about sampling the temperature every so often and writing it down

12. Measuring Some Changing Quantity In a lot of engineering problem we need to measure some quantity that changes over space or time. Think about how the temperature outside changes We can think about sampling the temperature every so often and writing it down

13. Measuring Some Changing Quantity The temperature or any quantity can also change spatially

14. Measuring Some Changing Quantity For our measurements we will be sampling quantities like acceleration, force, pressure at rates somewhere in the thousands of samples per second range.

15. Measuring Some Changing Quantity For our measurements we will be sampling quantities like acceleration, force, pressure at rates somewhere in the thousands of samples per second range. Rather then looking at a thermometer or a pressure gauge and writing down the temperature or pressure

16. Measuring Some Changing Quantity For our measurements we will be sampling quantities like acceleration, force, pressure at rates somewhere in the thousands of samples per second range. Rather then looking at a thermometer or a pressure gauge and writing down the temperature or pressure

17. Measuring Some Changing Quantity For our measurements we will be sampling quantities like acceleration, force, pressure at rates somewhere in the thousands of samples per second range. Rather then looking at a thermometer or a pressure gauge and writing down the temperature or pressure

18. Measuring Some Changing Quantity For our measurements we will be sampling quantities like acceleration, force, pressure at rates somewhere in the thousands of samples per second range. Rather then looking at a thermometer or a pressure gauge and writing down the temperature or pressure We use sensors that produce voltage signal that is related to the quantities we are interested in

19. Measuring Some Changing Quantity For our measurements we will be sampling quantities like acceleration, force, pressure at rates somewhere in the thousands of samples per second range. Rather then looking at a thermometer or a pressure gauge and writing down the temperature or pressure We use sensors that produce voltage signal that is related to the quantities we are interested in And digitally record the measurements on the computer at a regular interval

20. Sampling Frequency The time between measurements is called the sampling interval, and is generally measured in seconds, ms, micro sec, ns, ps.

21. Sampling Frequency The time between measurements is called the sampling interval, and is generally measured in seconds, ms, micro sec, ns, ps. The sampling frequency is the reciprocal of the sampling interval and is the number of samples per second Memorize this formula

22. Sampling Frequency The time between measurements is called the sampling interval, and is generally measured in seconds, ms, micro sec, ns, ps. The sampling frequency is the reciprocal of the sampling interval and is the number of samples per second Sampling frequency is described in Hertz. For example a digital audio is generally sampled at 44,100Hz or 44.1kHz

23. Digitizing a Continuous Signal Taken from Bishop

24. Digitizing a Continuous Signal You don’t have any information about what happens between samples when a continuously varying signal is digitized Taken from Bishop

25. Digitizing a Continuous Signal You don’t have any information about what happens between samples when a continuously varying signal is digitized You would like to know that the assumption “not much interesting” happened between samples is ok Taken from Bishop

26. Digitizing Levels Digitizers discritize signal to a signal to a finite number of levels within a range.

27. Digitizing Levels Digitizers discritize signal to a signal to a finite number of levels within a range. The number of levels always 2 to some power

28. Digitizing Range Digitizers discritize signal to a signal to a finite number of levels within a range. The range limits the largest and smallest signal you can capture

29. Dynamic Range smallest increment of voltage change that can be resolved by a digitizer is referred to the code width

30. Dynamic Range smallest increment of voltage change that can be resolved by a digitizer is referred to the code width The ratio of the total voltage range to the code width is the called the dynamic range.

31. Dynamic Range smallest increment of voltage change that can be resolved by a digitizer is referred to the code width The ratio of the total voltage range to the code width is the called the dynamic range. The dynamic range equal to

32. Dynamic Range smallest increment of voltage change that can be resolved by a digitizer is referred to the code width The ratio of the total voltage range to the code width is the called the dynamic range. The dynamic range equal to

33. Matlab and LabVIEW There are a lot of digital recording tools these days In this class we will mostly use LabVIEW BNC 2120

34. Matlab and LabVIEW There are a lot of digital recording tools these days In this class we will mostly use LabVIEW but you can also use Matlab by way of the headphone outputs and the Microphone inputs.

35. Time Vector In Matlab you will have to make a time vector to plot of audio signals. This is a vector the same length was the data that starts at zero. If the sampling frequency was 10kHz (10,000 samples per second) t = [0, 0.0001, 0.0002, 0.0003,…]

36. Matlab Handle Graphics Matlab has a hierarchal system that lets you control all aspects of a plot. This and other helpful things are described in the Matlab notes on the class webpage