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Low pass filter problem

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Hi 

  I am new to labview and i try to simulate a low pass filter operation, I used the attached VI but i always result in the output as zero . I was quite confused. 

I would like to know the problem in my VI.

 

 

wit regards,

sabarish

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@saillesh wrote:

Hi 

  I am new to labview and i try to simulate a low pass filter operation, I used the attached VI but i always result in the output as zero . I was quite confused. 

I would like to know the problem in my VI.

 

 

wit regards,

sabarish


Hey Sabarish,

 

I've applied a couple of fixes to your VI to make the Low Pass Filter function; it didn't need a lot of work, just some of the following changes:

 

Programmable LPF.png

 

  • In terms of the changes I've made to your block diagram, all I've done is create a signal which is compatible with the filter you've selected; for some reason this implementation will not pass out an uninitialised array, this will create the output we want. All that I do to create the signal using the Sine function with a couple of general wave parameters and pass it through to the LPF. The output signal from the LPF just needs to be bundled into a format acceptable by a graph; in terms of PhaseFrequency (Derived from the sampling rate to the LPF) and the Signal Value Array (1D) itself.

 

LPF2.png

 

  • The Low Pass Filter function you implemented doesn't seem to correspond appropriately to the dynamic data type which is output from your Simulate Signal Express VI. If you were to place an indicator at the output of the LPF in your VI, you'll see that it outputs an uninitialised array. Somewhere in this function, there's some incompatibility with the Dynamic data type. For a much easier implementation of the Low Pass Filter, you can drop a Filter Express VI which can deal with the dynamic data type, found in the Signal Analysis subpalette, as shown above.

 

From looking inside the LPF function, I've tried to find why the dynamic data type input would produce an uninitialised array output but as of yet I have no idea why it's outputting an uninitialised array. I'm going to do a little research and see what I can find, however I hope that for now this post will help you continue with your project.   


Alex Thomas, University of Manchester School of EEE LabVIEW Ambassador (CLAD)

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