Application design patterns represent LabVIEW code implementations and window, interacting with the scroll bars, and clicking the Abort button. LabVIEW. It should pull the coordinates of the OK button instead of hard-coding a coordinate I've used it before in LabVIEW when interfacing with a 3rd-party. National Instruments, NI, torentinonua.website, and LabVIEW are trademarks of National Instruments The menus and toolbar buttons available within the LabWindows/CVI. PLOAIE TORENTIALA DEVA If an interface-based resource. This review Splashtop Business consider Erectile theory: The Thunderbird to. Absolute control was to.
LabVIEW is one of the efficient system engineering software that Accumulates Information and process it for various reasons. More over, This professional application makes sure that customers can easily create blueprints. As, It can candlestick complicated control systems and separate equipment. After downloading this software, open this software.
I suppose your PC does not installed this software. Then, you can download this extension from ItTechGyan website. Now import that software file to your PC. Save my name, email, and website in this browser for the next time I comment. Skip to content. Download Here 6. Leave a Reply Cancel reply Comment. Enter your name or username to comment. Enter your email address to comment. Create a blank project. Save the project as Simple AAV. Add a waveform graph to the front panel window to display the acquired data.
Add a numeric indicator to the front panel window to display the average value. Note The terminals corresponding to the front panel window objects appear on the block diagram. Acquire a sine wave for 0. If you have hardware installed, follow the instructions in the Hardware Installed column to acquire the data using the DAQ Assistant. If you do not have hardware installed, follow the instructions in the No Hardware Installed column to simulate the acquisition using the Simulate Signal Express VI.
Drop dialog box. Type DAQ Assist in the text box and 2. Place the DAQ Assistant on the block 3. Wait for the DAQ Assistant dialog box 4. Wait for the Simulate Signal dialog box to open. Select Acquire Signals»Analog Input» 5. Select Sine for the signal type. Voltage for the measurement type. Select ai1 analog input channel 1 for 6. Set the signal frequency to Click the Finish button. In the Timing section, set the Samples per second Hz to In the Timing Settings section, select 8.
Automatic for the Number of samples. In the Timing Settings section enter 9. Enter in Rate Hz. In the Timing section, select the Simulate acquisition timing option. Click the OK button. Tip Reading samples at a rate of 1, Hz retrieves 0. Use the Statistic Express VI to determine the average value of the data acquired.
Note Future exercises do not detail the directions for finding specific functions or controls in the palettes. Use Quick Drop, the palette search feature, or the global search to locate functions and controls. Wire the data to the graph indicator. Note Future exercises do not detail the directions for wiring between objects. Save the VI. Test 1. Switch to the front panel window of the VI. Set the graph properties to be able to view the sine wave.
Click the Run button on the front panel toolbar to run the VI. The graph indicator should display a sine wave and the Average Value indicator should display a number around zero. If the VI does not run as expected, review the implementation steps. Close the VI. End of Exercise ni. Which function executes first: Add or Subtract?
Add b. Subtract c. Unknown 2. Which function executes first: Sine or Divide? Sine b. Divide c. Unknown 3. Which function executes first: Random Number, Divide or Add? Random Number b. Add d. Unknown 4. Which function executes last: Random Number, Subtract or Add? Unknown 5. If an input to a function is marked with a red dot known as coercion dot , what does the dot indicate? Data was transferred into a structure.
That input has not been wired c. The wire is broken d. The value passed into a node was converted to a different representation. Switch Until Released b. Switch When Released c. Latch When Pressed d. If the Run button appears broken when you finish wiring the block diagram, the VI is broken and cannot run. Required terminal is unwired. Control wired to another control. Broken subVI due to unwired required terminal. Debugging Tips The following table includes a few common problems to look for when debugging your VIs.
Is the numeric representation correct for your application? Do nodes execute in the correct order? Are there any hidden or unwired subVIs? To help avoid incorrect results caused by hidden VIs, specify that inputs to VIs are required. Execution Highlighting Single Stepping Probe Situation Debugging Tool Your VI is returning unexpected data and you Probe want to see intermediate values on the wires to find out where the problem initiates. You want to see how data moves from one node to the next on the block diagram.
You want to view each action of the VI on the block diagram. This tool slows down how fast the VI runs so you can see the data flow through the block diagram. Suspend the execution of a subVI to edit values of controls and indicators, to control the number of times it runs, or to go back to the beginning of the execution of the subVI.
When you reach a breakpoint during execution, the VI pauses and the Pause button appears red. Tip Always remember to turn this feature off when you are done debugging to free memory. NaN not a number a floating-point value that invalid operations produce, such as taking the square root of a negative number Inf infinity a floating-point value that valid operations produce, such as dividing a number by zero ni. Description The VIs in this exercise check the validity of a triangle and then calculate the area.
For a triangle to be valid, all three sides must have a length that is greater than zero. You can use this method when you know the lengths of all three sides of a triangle. Use single-stepping and execution highlighting to step through the VI. Open and examine the area and validity of a triangle VI. This VI takes input values for each of the three sides of a triangle, passes the values into a subVI that determines the area, and checks that the values entered are valid for a triangle.
Find and fix each error. The Details section describes the error and in some cases recommends how to correct the error. In the Area of Triangle VI, notice that the formula for calculating the area of a triangle requires the sum of the sides be divided by 2. Right-click the y input of the Divide function and select Create»Constant and enter a value of 2.
Save both VIs. Test the VI. These values are valid measurements for a triangle. Animate the flow of data through the block diagram. Notice that you can see how data flows through the wires. At the output of each node, you can see the data value displays momentarily. Because you have enabled the Retain Wire Values button, you can probe the last value in the wire. Probe the wire values. This displays the Probe Watch Window. The input values were all positive numbers, so that means the logic is incorrect.
Notice that the node returning a value of False is a Less than Zero? Notice that the Valid Triangle? Continue debugging the subVI. Execution highlighting shows the flow of data on the block diagram from one node to another. Nodes blink to indicate they are ready to execute.
Each time you click the Step Over button, the current node executes and pauses at the next node. The subVI is paused. Click the red pause button to resume the execution of the VI. You should see a tip strip with a value of You cannot take the square root of a negative number, which is why the Area of Triangle indicator returns NaN. Tip If you cannot see the tip strip, you can click the wire to open the Probe Watch window to see the value. If you look more closely, you notice that the inputs for the subtract function are reversed.
Test the Area of Triangle VI. Troubleshooting and Debugging VIs The square root function should return a value of For each set of test values, record the area you get when you run the VI. Save and close the VI when you are finished testing. Error Handling Objective: Describe the difference between automatic and manual error handling.
Change the configuration settings in the Tools»Options dialog box. Typically, functions use numeric error codes, and VIs use an error cluster, usually with error inputs and outputs. Use the error cluster controls and indicators to create error inputs and outputs in subVIs.
A non-zero error code is coupled with a status of FALSE signals a warning rather than an error 3 source—a string that identifies where the error occurred Errors and Warnings When an error occurs, open the Explain Error dialog box to see more information about the error. If no error is found, it returns the first warning.
At the end of your application after all error sources are merged into one error cluster, you must report errors to the user using the Simple Error Handler VI or another error reporting mechanism. Errors and Warnings Recommendations By default, the Simple Error Handler VI displays a dialog with a description of any errors that occurred and does not report warnings.
Which of the following will result in a broken run arrow? A subVI is broken b. The diagram includes a divide by zero c. A required subVI input is unwired d. A Boolean terminal is wired to a numeric indicator 2. Which of the following are components and data types of the error cluster? Status: Boolean b. Error: String c. Code: bit integer d. Source: String 3.
All errors have negative error codes and all warnings have positive error codes. True b. False 4. Merge Errors function concatenates error information from multiple sources. Loops Review Objective: Recognize loop structures and explain how to use them.
If you use a While Loop, what is the condition that you need to stop the loop? If you use a For Loop, how many iterations does the loop need to run? Is it easier to implement a For Loop or a While Loop? Scenario 2 Acquire pressure data until the pressure is greater than or equal to psi. Scenario 3 Acquire pressure and temperature data until both values are stable for two minutes.
Scenario 4 Output a voltage ramp starting at zero, increasing incrementally by 0. For Loops - Answers Scenario 1 Acquire pressure data in a loop that executes once per second for one minute. For Loop: 60 iterations 3. Both are possible Scenario 2 Acquire pressure data until the pressure is greater than or equal to psi. For Loop: unknown 3. A While Loop. Although you can add a conditional terminal to a For Loop, you still need to wire a value to the count terminal.
Without more information, you do not know the appropriate value to wire to the count terminal. For Loop: 11 iterations Including the two end points, count the iteration for each value - 0, 0. Both are possible. While Loops Objective: Recognize tunnels and explain their purpose on a loop structure and demonstrate how to use error checking and error handling inside a loop.
Tunnels Tunnels transfer data into and out of structures. Data pass out of a loop after the loop terminates. Error Checking and Error Handling You can wire an error cluster to the conditional terminal to stop the iteration of the loop. If an error occurs, the loop stops.
Using Loops Scenario Create a VI that continuously generates random numbers between 0 and until it generates a number that matches a number selected by the user. Determine how many random numbers the VI generated before generating the matching number. The flowchart in Figure illustrates the data flow for this design. Create a blank project and save it as Auto Match. Create a new VI in the project and save it as Auto Match.
Build the front panel shown in Figure Set the properties for the Number to Match control so that the data type is a bit unsigned integer, the data range is from 0 to , the increment value is 1, and the digits of precision is 0. Set the representation of the Current Number indicator to an unsigned, bit integer and set the digits of precision for the Current Number output to 0. Using Loops Figure Create the block diagram shown in Figure Enter a value of Because the Random Number function generates a double-precision, floating point number between 0 and 1, multiplying the number by produces a range of numbers between 0 and Otherwise, it returns TRUE.
In this case, the output from Round To Nearest is a double-precision, floating point but Current Number is an integer. Update the VI to remove the coercion dots. This inserts the To Unsigned Long Integer function on the wire. Notice that converting the output from the Round To Nearest function removes all the coercion dots on the block diagram, as shown in Figure Completed Auto Match VI 9.
Display the front panel. Note If synchronous display is enabled, then every time the block diagram sends a value to the Current Number indicator, the block diagram stops executing until the front panel has updated the value of the indicator. In this exercise, you enable the synchronous display, so you can see the Current Number indicator get updated repeatedly on the front panel. Typically, the synchronous display is disabled to increase execution speed since you usually do not need to see every single updated value of an indicator on the front panel.
Change the number in the Number to Match control to a number that is in the data range, which is 0 to with an increment of 1. Run the VI. Change the Number to Match value and run the VI again. Current Number updates at every iteration of the loop because it is inside the loop. Number of Iterations updates upon completion because it is outside the loop. To see how the VI updates the indicators, enable execution highlighting. Run the VI and observe the data flow. Turn off execution highlighting to quickly finish executing the VI.
Try to match a number that is outside the data range. For Loops Objective: Demonstrate how to add a conditional terminal to a For Loop and describe how numeric conversion occurs on the For Loop count terminal. Conditional Terminal You can add a conditional terminal to configure a For Loop to stop when a Boolean condition or an error occurs.
A For Loop with a conditional terminal executes until the condition occurs or until all iterations are complete, whichever happens first. The following For Loop generates a random number every second until seconds has passed or until the user clicks the stop button. Count Terminal Numeric Conversion If you wire a double-precision, floating-point numeric value to the count terminal, LabVIEW converts the numeric value to a bit signed integer.
When a loop finishes executing an iteration, it immediately begins executing the next iteration, unless it reaches a stop condition. If you are acquiring data, and you want to acquire the data once every 10 seconds, you need a way to time the loop iterations so they occur once every 10 seconds. You also want to time a loop to provide the processor with time to complete other tasks, such as processing the user interface.
Wait Functions Inside a Loop Use a wait function inside a loop to accomplish the following actions: Wait Function Behavior Wait Until Next ms Multiple Monitors a millisecond counter and waits until the millisecond counter reaches a multiple of the amount you specify. This function is synced to the system clock. Wait ms Waits until the millisecond counter counts to an amount equal to the input you specify Time Delay Express VI Similar to the Wait ms function with the addition of built-in error clusters.
This timing diagram assumes that the wait functions begin running immediately for each loop iteration and that the loop is ready to iterate as soon as the wait function finishes. Data Feedback in Loops Objective: Apply shift registers when appropriate and predict the correct value at different iterations of the loop. If you do not initialize the register, the loop uses the value written to the register when the loop last executed or it uses the default value for the data type if the loop has never executed.
You can add more than one shift register to a loop for applications such as averaging data points. Demonstration: Creating Shift Registers Replace tunnels with shift registers when you need to transfer values from one loop iteration to the next. If you convert a tunnel with auto-indexing enabled to a shift register on a While Loop, the wire to any node outside the loop breaks because shift registers cannot auto-index ni.
Modify the VI to average the last five temperature measurements and display the running average on the waveform chart. Notice the variation in the simulated temperature reading. Stop the VI by clicking the Stop button on the front panel. Modify the VI to reduce the number of temperature spikes.
Drag the lower resizing handle of the shift register to display four shift registers. The Thermometer Demo VI returns one temperature measurement and initializes the left shift registers before the loop starts. Resize the function to have five terminals. Note You can create stacked shift register terminals on the left side of a loop to remember multiple previous iterations and carry those values to the next iterations. This technique is useful for averaging data points. Stacked shift registers can occur only on the left side of the loop because the right terminal transfers the data generated from only the current iteration to the next iteration.
The VI adds this value to the last four measurements stored in the left terminals of the shift register. The VI divides the result by five to find the average of the five measurements—the current measurement plus the previous four. The VI displays the average on the waveform chart. Notice that the VI initializes the shift register with a temperature measurement. Save and close the VI and the project.
Plotting Data Objective: Use data feedback in a loop to plot waveform charts. Waveform Chart The waveform chart is a special type of numeric indicator that displays one or more plots of data typically acquired at a constant rate. Waveform charts can display single or multiple plots. Using Loops Scenario Modify the VI from Exercise to plot both the current temperature and the running average on the same chart. In addition, allow the user to examine a portion of the plot while the data is being acquired.
Design Figure shows the front panel for the existing Temperature Monitor VI and Figure shows the block diagram. Also, expand the legend to show additional plots. To modify the block diagram in Figure , you must modify the chart terminal to accept multiple pieces of data. Use a Bundle function to combine the average temperature and the current temperature into a cluster to pass to the Temperature History terminal. Modify the block diagram so that it resembles Figure Modify the front panel so that it resembles Figure Double-click the label to edit the plot names.
The order of the plots listed in the plot legend is the same as the order of the items wired to the Bundle function on the block diagram. Click the plot icon, select Common Plots from the menu, and choose the plot you want. Use the tools in the scale legend and the graph palette to examine the data as it generates. Close the VI and project when you are finished.
Which structure must run at least one time? While Loop b. Arrays Objective: Identify when to use arrays and learn how to create and initialize arrays. Arrays Array Collection of data elements that are of the same type. Elements The data that make up the array. Elements can be numeric, Boolean, path, string, waveform, and cluster data types. Dimension Length, height, or depth of the array. Arrays can have one or more dimensions and as many as -1 dimensions. The index of the first element in the array, regardless of its dimension, is zero.
Index is zero-based, which means the range is 0 to n - 1, where n is the number of elements in the array. March is the third month, so it has an index of 2. It requires a column index and a row index to locate an element, both of which are zero-based. Initializing Arrays An uninitialized array contains a fixed number of dimensions but no elements. An initialized defines the number of elements in each dimension and the contents of each element.
To create an array constant on the block diagram, select an array constant on the Functions palette, place the array shell on the block diagram, and place a string constant, numeric constant, a Boolean constant, or cluster constant in the array shell.
Restrictions You cannot create arrays of arrays. However, you can use a multidimensional array or create an array of clusters where each cluster contains one or more arrays. Also, you cannot create an array of subpanel controls, tab controls,. Common Array Functions Objective: Create and manipulate arrays using built-in array functions.
Multimedia: Common Array Functions Functions you can use to manipulate arrays are located on the Array palette. Initialize Array Creates an n-dimensional array in which every element is initialized to the value of element. Insert Into Array Inserts an element or subarray at the point you specify in index.
Search 1D Array Searches for an element in a 1D array starting at start index. Because the search is linear, you need not sort the array before calling this function. LabVIEW stops searching as soon as the element is found. Determine what belongs in the highlighted section. Polymorphism Objective: Understand the ability of various VIs to accept input data of different data types.
Polymorphism Polymorphism The ability of VIs and functions to automatically adapt to accept input data of different data types. Functions are polymorphic to varying degrees—none, some, or all of their inputs can be polymorphic. Auto-Indexing Objective: Use auto-indexed inputs and outputs to create graphs and arrays. Auto-indexing The ability to automatically process every element in an array.
Auto-Indexing If you wire an array to or from a For Loop or While Loop, you can link each iteration of the loop to an element in that array by enabling auto-indexing. The tunnel image changes from a solid square to the image to indicate auto-indexing. Waveform Graphs A waveform graph collects the data in an array and then plots the data to the graph. For example, consider the following block diagram.
The array Input Array contains the following elements: 7, 2, 0, 3, 1, 9, 5, and 7. Because of the conditional tunnel, the Values less than 5 array contains only the elements 2, 0, 3, and 1 after this loop completes all iterations.
If you wire an array to an auto-indexing tunnel on a For Loop, you do not need to wire the count N terminal. I 1 2 1 The For Loop executes the number of times equal to the number of elements in the array. Auto-Indexing Input—Different Array Sizes If the iteration count terminal is wired and arrays of different sizes are wired to auto-indexed tunnels, the actual number of iterations becomes the smallest of the choices.
I 1 1 The For Loop iterates 5 times and because the iterations are zero-based, the output is 4. The front panel of this VI is built. You complete the block diagram to practice several different techniques to manipulate arrays. Implementation 1. Open Manipulating Arrays. The front panel, shown in Figure , is already built for you. Open the block diagram and complete each of the cases that correspond to the tabs on the front panel as shown in Figures through Switch to the front panel and test the Concatenate Channels case.
Stop the VI. Boolean control is False, the array elements are added. Note This case demonstrates polymorphic functionality by adding and subtracting elements of the array. Switch to the block diagram and select the Select a Channel case. Complete the Select a Channel case as shown in Figure The output from this function is a 1D array and is the waveform you select with the Select Channel control. Switch to the front panel and test the Select a Channel case. Switch to the block diagram and select the Waveform Data case.
Complete the Waveform Data case block diagram as shown in Figure The waveform datatype is a special kind of cluster that contains additional timing information about the waveform. Notice the value from the Offset control must be coerced to be used with the waveform datatype. Note Polymorphism is the ability of VIs and functions to automatically adapt to accept input data of different data types, including arrays, scalars, and waveforms. VIs and functions are polymoprhic to varying degrees.
Switch to the front panel and test the Waveform Data case. Switch to the block diagram and select the All Data Channel case. Complete the All Data Channel case as shown in Figure Each 1D array becomes a row in the 2D array. In this exercise, you have 2 elements of data for the number of rows and columns. Note The polymorphic functionality of LabVIEW functions allows you to perform the same operation on each element without extracting the Lesson 5 array elements, as you do with the two Add functions in the All Data Channel case.
Switch to the front panel and test the All Data Channel case. Switch to the block diagram and select the Waveform Subset case. Complete the Waveform Subset case as shown in Figure In this exercise, you use this function to zoom in on a subset of the waveform you generated.
The default value is set to start at element 0. The default value is set to output elements. Switch to the front panel and test the Waveform Subset case. The x-axis starts at zero because the VI creates a brand new array and the graph does not know where the data was located in the original array.
Example VIs can show you how to use specific functions and programming concepts such as arrays and polymorphism. Complete the following steps to use the NI Example finder to locate example VIs that demonstrate different ways to use the Array function. Click the Search tab and enter the keyword array. Click the Search button to find VIs using that keyword.
Click one of the example VIs in the search results list and read the description. Double-click an example VI to open it. Read through the comments on the front panel and block diagram to learn more about what this example VI demonstrates. Run the example, examine the different cases, and click the Stop button to exit. Clusters Objective: Identify when to use clusters and be able to create them. Clusters Clusters Clusters group data elements of mixed types A cluster is similar to a record or a struct in text-based programming languages.
Clusters vs. The element can be a numeric, Boolean, string, path, refnum, array, or cluster control or indicator. Cluster Order Cluster elements have a logical order unrelated to their position in the shell. The cluster order determines the order in which the elements appear as terminals on the Bundle and Unbundle functions on the block diagram. You can view and modify the cluster order by right-clicking the cluster border and selecting Reorder Controls In Cluster from the shortcut menu.
The number of output terminals does not depend on the number of elements in the input cluster. Use Bundle when some or all cluster elements are unnamed. I ni. If the elements that are bundled have labels, you can access them using the Unbundle By Name function. Otherwise use the Unbundle function. The Build Array function is used to create multi-plot waveform graphs.
LabVIEW uses error clusters to pass error information. Scenario Another developer has created a VI that displays temperature warnings. This VI is part of the temperature weather station project studied throughout this course.
Your task is to update this VI to use clusters instead of individual terminals for inputs and outputs. Yes Warning? You modify the Temperature Warnings VI to receive and return data in the form of that same cluster as shown in Figure The modified VI works in a more modular fashion with other subVIs in the overall application.
Open Weather Warnings. Place existing controls and indicators in a cluster named Weather Data as shown in Figure Resize the cluster so that all the elements are visible and arranged vertically as shown in Figure Reorder the items in the cluster as shown in Figure Reorder Cluster ni. Modify the VI to receive and return cluster data. Rename the copy Weather Data In.
Rename the indicator Weather Data Out. Modify the block diagram as shown in Figure to extract data from the input cluster. Temperature Warnings with Clusters Block Diagram ni. Wire the outputs of the Unbundle By Name function to the broken wires in the order shown. Because you moved individual controls and indicators into a single cluster, you must use the Unbundle By Name function to wire the internal controls and indicators independently of each other.
Display two elements and use the Operating tool to select Warning? Connect the broken wires to the Unbundle By Name inputs as shown. Note If the order of the elements in the Unbundle By Name and the Bundle By Name functions is different than what you want, you can use the Operating tool to change the order. Save and close the Temperature Warnings VI. Run the VI and verify that the Weather Data indicator displays correct values. Type Definitions Objective: Identify and determine when to use a type definition, strict type definition, or control.
Control Options Use custom controls and indicators to extend the available set of front panel objects and to make them available on other front panels. Changes made to one control does not reflect in other controls. Scenario As a LabVIEW developer, you can encounter situations where you need to define your own custom data types in the form of clusters and enums.
A challenge associated with using custom data types is that you may need to change them later in development. In addition, you may need to change them after they have already been used in VIs. For example, you create copies of a custom data type and use them as controls, indicators, or constants in one or more VIs. Then you realize that the custom data type needs to change. You need to add, remove, or change items in the cluster data type or the enum.
Usually, you want all the copies of the custom data type to update if you update the original custom data type. To achieve this you need copies of the custom data types to be tied to a type definition, which is defined as follows: Type definition—A master copy of a custom data type that multiple VIs can use. Implementation In this exercise, you modify the Temperature Warnings VI that you revised in Exercise in such a way that the changes to the Weather Data custom data type propagate through the application.
When complete, the Weather Station application monitors temperature and wind information. This exercise modifies the Temperature Warnings VI. Experiment with changing an existing cluster. Make a type definition. The window looks like the front panel of a VI but it does not have a block diagram. This indicates that the indicator is not tied to the type definition. Tie the Weather Data Out indicator to the type definition. Note You can no longer add or remove elements to or from the cluster control and indicator on the front panel.
You must open the type definition and add or remove the element from the control editor window. Edit the Weather Data type definition to include unit information. Creating and Leveraging Data Structures Figure Right-click the enum and select Edit items. Create an item for Celsius and Fahrenheit.
Arrange the front panel of the VI as shown in Figure Open the Windspeed Warnings VI. Creating and Leveraging Data Structures 5. Modify the Weather Data type definition with windspeed controls as shown in Figure Modify the block diagram of the Windspeed Warnings VI to use the new Weather Data type definition instead of individual controls and indicators, as shown in Figure You can create an array of arrays. False 2.
You have two input arrays wired to a For Loop. Auto-indexing is enabled on both tunnels. One array has 10 elements, the second array has five elements. A value of 7 is wired to the Count terminal, as shown in the following figure. What is the value of the Iterations indicator after running this VI?
Which of the following custom control settings defines the data type of all instances of a control but allows for different colors and font styles? Control b. Type Definition c. Strict Type Definition d. Cluster control 4. In the future, you might need to modify your data to include the color of the circle U What data structure should you use to represent the circle in your application? Three separate controls for the two positions and the radius.
A cluster containing all of the data. A custom control containing a cluster. A type definition containing a cluster. An array with three elements. False You cannot drag an array data type into an array shell. However, you can create two-dimensional arrays. This helps to protect against programming error. LabVIEW mathematical functions work the same way—if you wire a 10 element array to the x input of the Add function, and a 5 element array to the y input of the Add function, the output is a 5 element array.
Although the for loop runs 5 times, the iterations are zero based, therefore the value of the Iterations indicators is 4. Case Structures Objective: Recognize and use the basic features and functionality of Case Structures. Activity Case Structures Review Figure What is the purpose of the Case Structure? Execute one of its subdiagrams based on an input value b.
Repeat a section of code until a condition occurs c. Execute a subdiagram a set number of times 2. How many of its cases does a Case Structure execute at a time? All of them b. One 3. What is the purpose of the Case Selector Label? Lets you wire an input value to determine which case executes b.
Show the name of the current state and enable you to navigate through different cases 4. What is the purpose of the Selector Terminal? Show the name of the current state and enable you to navigate through different cases Demonstration: Case Structures Right-click the Case structure to display the shortcut menu.
The shortcut menu gives you options for configuring a Case structure. The Case structure configuration changes based on the type of data that you connect. Integer Case Structure has any number of cases. Specify a Default case. The numeric representation of the integer input will determine the range of possible values for the Case Selector Label. You can specify ranges of values for the Case Selector Label. Use Radix option in shortcut menu to specify whether the Case Selector Label displays values in decimal, hexadecimal, octal, or binary.
String Case Structure has any number of cases. By default, string values are case sensitive. Shortcut menu includes option for Case Insensitive Match for the string text. Wire an error cluster to the terminal to execute code if there is no error and skip code if there is an error. Input and Output Tunnels As with other types of structures, you can create multiple input and output tunnels.
Right-click on the tunnel and select Use Default if Unwired. Using Decision-Making Structures Scenario You created a VI where a user inputs a temperature, a maximum temperature, and a minimum temperature. A warning string generates depending on the relationship of the given inputs. However, a situation could occur that causes the VI to work incorrectly. For example, the user could enter a maximum temperature that is less than the minimum temperature.
Set the Warning? Otherwise, the VI does not execute the code. Instead, the VI generates a new string and the Warning? Open Temperature Warnings. Open the block diagram and create space to add the Case structure. Using Decision-Making Structures 4. Modify the block diagram similar to that shown in Figure , Figure , and Figure This VI is part of the temperature weather station project. Make sure the Less? By default, the Case structure has True and False cases. These cases change to Error and No Error cases only after you wire Error In to the selector terminal.
Click the case selector label to choose the True case. Enter the text in the String Constant. Switch to the front panel of the VI. Boolean value for each set of data. Test the Error case. Test the Error case to make sure that this VI can output the error information it receives.
The error information you entered passes through the Error case in the VI and is output in the Error Out cluster. Save and close the VI. Event-Driven Programming Objective: Recognize basic features and functionality of event structures. Demonstration: Event-Driven Scenario Event-driven Method of programming where the program waits on an event to occur before programming executing the code written to handle that event. Event An asynchronous notification that something has occurred.
In this course, you will only learn about user interface events, which include mouse clicks, key presses, and value changes of a control. Polling Versus Events Polling Event ni. LabVIEW has already performed the default action associated with that event. You also can discard the event entirely to prevent the change from affecting the VI. Note A single case in the Event structure cannot handle both notify and filter events. A case can handle multiple notify events but can handle multiple filter events only if the event data items are identical for all events.
Next, you modify the polling VI to create a more efficient, event-driven VI and observe the changes in behavior. Finally, you add different types of events to the VI. Panel Close? Handles the event in which the user tries to close the running VI by clicking the window close button.
Observing the Polling VI Behavior 1. Open and run Polling. Open the block diagram, turn on execution highlighting, and run the VI again. Notice how often the Time Check terminal sends data to the Case structure and how often the While Loop iterates. Stop the VI and turn off execution highlighting. Close Polling. Open the block diagram of UI Event Handler. You move these terminals into the appropriate event cases later in this exercise.
Delete the Case structure and clean up any broken wires. Place an Event structure inside the While Loop between the iteration terminal and the conditional terminal. Configure the event as shown in Figure Configuring the "Stop": Value Change Event ni. Click OK to close the dialog box. Place a True constant inside the new "Stop": Value Change event and wire it to the conditional terminal of the While Loop as shown in Figure Click the item and select NewVal.
Notice that the Iteration indicator does not increment. Switch to the block diagram and enable execution highlighting. Notice that the While Loop is executing the first iteration. The Event structure is waiting for an event. Disable execution highlighting and switch back to the front panel. Click the Stop button to stop the VI. Notice that the VI stops running even though the Stop button is disconnected. Notice that the Stop button stays depressed even though the mechanical action is set to Latch When Released.
The reason the button stays depressed is because the VI stopped running after you clicked the button. Reset the Stop button by clicking it again.
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Additionally, I've tried the same code with a for loop originally via a conditional terminal so it could stop early and that didn't work either. Thanks for any help I appreciate it! Option 1. You can right click the Event Structure and select "Edit events handled by this case" dialog and then uncheck the "Lock panel" checkbox -- that will allow the UI to be live while you are in that frame.
I do not recommend this solution generally unless you have an extremely simple user interface because it leads to the user being able to change controls without the events behind those controls being processed not a good UI experience for users. But if the UI is simple enough, that works. Option 2. You can create a user event that is the code you want inside your While Loop.
Do the same thing in the user event case so that the event re-triggers itself if and only if the Abort button has not been pressed. Option 3. The other loop moves into various states at the request of the UI loop You can Google "queued message handler" for extensive details of this solution. This is the most common solution for complex UI requirements, especially useful for separating concerns of the UI code from the execution code. Results from the Developer Survey are here. Stack Overflow for Teams — Start collaborating and sharing organizational knowledge.
Create a free Team Why Teams? Learn more. Asked 1 year ago. Modified 1 year ago. Viewed 1k times. This is what the front panel is configured too for completeness: Essentially what I want to happen is the while loop to execute when I press DWG and in the middle of the cycle be able to abort it. Geo Geo 33 4 4 bronze badges. Add a comment. Sorted by: Reset to default. Highest score default Date modified newest first Date created oldest first. Thanks for you're informative reply! Really, you just need to educate them to the potential hazards of using abort and that is why you don't show it.
Dittos dittos dittos. Abort prevents the remaining code from completing, including any safety shutdown routines, file closings, power-downs, etc. That is all the ammo you need. I know NI is working hard to prevent those things to happen, but once in a while once a year I see this happening to a colleague who refuses to use an event structure Just make you don't just hide the toolbar, also disable the abort button other wise ctrl-.
Abort means "halt whatever you're doing, cleanup, and return to idle state to await the next command". An unknown state of the hardware can leave it unaccessible until you power cycle the equipment. You could argue safety regulations and standard industry practices without much effort. And you could always include removing them in ISO proceedures.
I also found from ni. Link to comment. Shaun Hayward Posted August 10, Posted August 10, edited. Edited August 10, by Shaun Hayward. Ditto Shaun! Ditto crossrulz! Ton Plomp Posted August 10,
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