In this exercise I’m going to explain how to read data from three different tables (temperature, pression and wind speed) from an Access database and then showing them in a multiplot waveform with LabView. The program will also allow us to create and delete tables.
In this practice I’m going to explain how to show in a Labview VI the waveform of the charge and discharge of a capacitor using the data acquisition provided by NI-DAQ 6008. The NI-DAQ is a device which allows us the digital-to-analog and analog-to-digital conversion.
Here I’m going to explain how to use the DLL call to use with the LABVIEW library CALC.dll to make a multiplication operation.
These functions are used when you want one VI or part of a block diagram to wait until another VI or part of a block diagram finishes a task without forcing LabVIEW to poll.
Use the Semaphore VIs to limit the number of tasks that can simultaneously operate on a shared (protected) resource. A protected resource or critical section of code might include writing to global variables or communicating with external instruments.
You can use the Semaphore VIs to synchronize two or more separate, parallel tasks so that only one task at a time executes a critical section of code protected by a common semaphore. In particular, use these VIs when you want certain VIs or parts of a block diagram to wait until another VI or part of a block diagram is finished with the execution of a critical section.
|Acquire Semaphore||Acquires access to a semaphore.|
|Get Semaphore Status||Returns current status information of a semaphore.|
|Not A Semaphore||Returns TRUE if semaphore is not a valid semaphore refnum.|
|Obtain Semaphore Reference||Obtains a reference to an existing semaphore or creates a new semaphore and returns a reference to that semaphore.|
|Release Semaphore||Releases access to a semaphore. If the Acquire Semaphore VI is waiting for the semaphore this VI releases, it stops waiting and continues execution.|
|Release Semaphore Reference||Releases a reference to a semaphore.|
Then you can see the VI I’ve built with this sinchronization tool:
– FRONT PANEL –
– FRONT PANEL (WHEN STARTED) –
– FRONT PANEL (2 sec. SINCHRONIZATION)
– BLOCK DIAGRAM –
To download the VI: