AHMET OZMEN

1. AHMET OZMEN

2. Virtual Instruments (VIs) • LabVIEW programs are called virtual instruments, or VIs • Appearance and operation imitate physical instruments, such as oscilloscopes and digital multimeters

3. Parts of a VI LabVIEW VIs contain three main components: • Front Panel • Block Diagram • Icon/Connector Pane

4. The LabVIEW Environment “VI” = program or function “Front Panel” = user interface “Block Diagram” = code

5. Front Panel-Controls & Indicators • Knobs/Dials • Graphs/Charts • Buttons • Digital Displays • Sliders • Thermometers • Customize and create your own

6. Front Panel – Controls Palette • Contains the controls and indicators you use to create the front panel • Access from the front panel by selecting View»Controls Palette

7. Front Panel – Front Panel Toolbar

8. Block Diagram Block diagram objects include the following: • Terminals • SubVIs • Functions • Constants • Structures • Wires

9. Block Diagram – Functions Palette • Contains the VIs, functions, and constants you use to create the block diagram

10. Block Diagram – Block Diagram Toolbar

11. Block Diagram Terminals

12. Searching for Controls, VIs & Functions • Find controls, function, and VIs using the Search button on the Controls and Functions palette

13. Dataflow LabVIEW follows a dataflow model for running VIs • A node executes only when data are available at all of its input terminals • A node supplies data to the output terminals only when the node finishes execution

14. Dataflow Programming Block Diagram 1 2 3 Both Simulate Signal Express VIs execute simultaneously 1 Comparison waits until all inputs are present, then executes 2 Once executed, output from comparison continues through code 3

15. Building a Simple VI

16. Building a Simple VI – Acquire Acquire Express VIs: • DAQ Assistant Express VI • Instrument I/O Assistant Express VI • Simulate Signal Express VI • Read from Measurement File Express VI

17. Building a Simple VI – Analyze Analyze Express VIs: • Amplitude and Level Measurements Express VI • Statistics Express VI • Spectral Measurements Express VI • Tone Measurements Express VI • Filter Express VI

18. Built-in Programming Assistance Highlight Execution Block Diagram Cleanup Context Help

19. PC-BasedData Acquisition (DAQ)

20. DAQ Demo

21. While Loops Repeat (code); Until Condition met; End; LabVIEW While Loop Flowchart Pseudo Code

22. While Loops • Iteration terminal: returns number of times loop has executed; zero indexed • Conditional terminal: defines when the loop stops Iteration Terminal Conditional Terminal

23. While Loops – Tunnels • Tunnels transfer data into and out of structures • The tunnel adopts the color of the data type wired to the tunnel • Data pass out of a loop after the loop terminates • When a tunnel passes data into a loop, the loop executes only after data arrive at the tunnel

24. While Loops - Error Checking and Error Handling • Use an error cluster in a While Loop to stop the While Loop if an error occurs

25. For Loops N=100; i=0; Until i=N: Repeat (code;i=i+1); End; LabVIEW For Loop Flowchart Pseudo Code

26. For Loops • Create a For Loop the same way you create a While Loop • If you need to replace an existing While Loop with a For Loop, right-click the border of the While Loop, and select Replace with For Loop from the shortcut menu • The value in the count terminal (an input terminal) indicates how many times to repeat the subdiagram

27. Timing a VI Why do you need timing in a VI? • Control the frequency at which a loop executes • Provide the processor with time to complete other tasks, such as processing the user interface

28. Timing a VI – Wait Functions • A wait function inside a loop allows the VI to sleep for a set amount of time • Allows the processor to address other tasks during the wait time • Uses the operating system millisecond clock

29. Timing Methods • Wait Until Next Multiple VI – Variable time of execution • Execute A, Execute B, sleep until OS timer reaches next multiple of 20 ms • Wait VI – Constant time of execution • Execute A, Execute B, sleep 10 ms

30. Timing a VI – Elapsed Time Express VI • Determines how much time elapses after some point in your VI • Keep track of time while the VI continues to execute • Does not provide the processor with time to complete other tasks

31. Iterative Data Transfer – Shift Registers • Right-click the border and select Add Shift Register from the shortcut menu • Right shift register stores data on completion of an iteration • Left shift register provides stored data at beginning of the next iteration

32. Case Structures • Have two or more subdiagrams or cases • Execute and displays only one case at a time • An input value determines which subdiagram to execute • Similar to case statements or if...then...else statements in text-based programming languages

33. Case Structures • Case Selector Label: contains the name of the current case and decrement and increment buttons on each side • Selector Terminal: Wire an input value, or selector, to determine which case executes

34. Case Structures – Default Case • You can specify a default case for the Case structure • If you specified cases for 1, 2, and 3, but you get an input of 4, the Case structure executes the default case • Right-click the Case structure border to add, duplicate, remove, or rearrange cases and to select a default case

35. State Programming Although Sequence structures or sequentially wired subVIs accomplish the purpose, it is not always the best choice: • What if you need to change the order of the sequence? • What if you need to repeat one item in the sequence more often than the other items? • What if some items in the sequence execute only when certain conditions are met? • What if you need to stop the program immediately, rather than waiting until the end of the sequence?

36. State Machines • The state machine design pattern implements a state diagram or flow chart • When to use state machines? • Commonly used to create user interfaces, where different user actions send the user interface into different states • Commonly used for process tests, where a state represents each segment of the process

37. State Machines – Infrastructure • A state machine consists of a set of states and a transition function that maps to the next state • Each state can lead to one or multiple states or end the process flow While Loop Case Structure Shift Register

38. State Machines – Default Transition

39. Parallelism • Often, you need to program multiple tasks so that they execute at the same time • In LabVIEW, tasks can run in parallel if they do not have a data dependency between them, and if they do not use the same shared resource • An example of a shared resource is a file, or an instrument

40. Automatic Multithreading in LabVIEW • LabVIEW automatically divides each application into multiple execution threads (introduced in 1998 with LabVIEW 5.0) • Parallel code paths will execute in unique threads thread thread thread

41. Multiple Loop Architectures

42. TriggeredAcquisitionDemo

43. THANK YOU!