Learn LabVIEW DSP in 3 Hours - Example 2: Integrating Simple Filters

LabVIEW DSP has new features like LabVIEW Project

To learn more about this feature follow the link below for step-by-step instructions.

Using the LabVIEW Project with LabView DSP Module

Complete the following steps to apply a Lowpass filter to a simulated a sine wave, and to display the filtered signal in time and frequency domains.

1. Switch the execution target back to NI SPEEDY-33 by choosing Operate»Switch Execution Target»SPEEDY33 from the menu.
2. Open the Example 1.vi that you built in previous example of this tutorial. Select File»Save As and rename the VI to Example 2.vi.
3. Modify the front panel as shown in the following figure.
   
   
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   Figure 1. Front Panel of Example 2.vi
   
   
   1. Create a copy of Input Signal – Time Domain waveform graph (by holding down Ctrl and dragging the graph). Review the Properties of the new graph and note that it has the same x and y scales as Input Signal – Time Domain graph. Label the new graph Filtered Signal – Time Domain.
   2. Create a copy of Input Signal – Frequency Domain waveform graph (by holding down Ctrl and dragging the graph) and label the new graph Filtered Signal – Frequency Domain.
      
      
4. Modify the block diagram as follows.
   
   
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   Figure 2. Block Diagram of Example 2.vi
   
   
   1. Place a Filter Express VI from Functions»Signal Processing»Filters palette to apply a Lowpass filter to the signal. Double click on the VI and configure it by entering 1000 for Cutoff Frequency, and selecting Infinite impulse response (IIR) filter with Chebyshev topology of order 5. Display the filtered signal by wiring the Filtered Signal output of the Express VI to Filtered Signal – Time Domain terminal.
      
      
      Figure 3. Configuration Window for Filter Express VI
      
      
   2. Create another copy of the Spectral Measurements Express VI by dragging it while holding the Ctrl key. Wire the Filtered Signal output of the Filter VI to the Signals input of Spectral Measurements. Then connect the FFT - (Peak) output to Filtered Signal – Frequency Domain terminal to display the frequency component of the filtered signal.
      
      
5. Run the VI. Notice that as you increase the frequency beyond 1000Hz, the signal is attenuated.
6. Save and close Example 2.vi.

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