Swept filter test

[bjmcclellan]

I am starting to develop an application to test a low-pass filter assembly. I need to sweep from 0.1 to 100 hertz. I don't need to sweep the entire range but am interested in maybe a dozen or so frequencies. Can I use an array of values to generate each frequency in succession, holding each for a couple of cycles to get a stable measurement? I am using a USB-6221 for the DAQ.

Any suggestions of pointers to existing examples would be most greatly appreciated.

Thanks

[Anjelica-W]

You can use property nodes to change the values of the frequency and duty cycle. The following KnowledgeBase article and example provide more information on this topic.

http://digital.ni.com/public.nsf/allkb/82C9F3C15F62974E86256EBA0058CAF5?OpenDocument

https://decibel.ni.com/content/docs/DOC-8382

[bjmcclellan]

I will try that in my code.

Thanks!

[bjmcclellan]

I'm not quite sure where to put the property node. I've been cramming to understand Labview but am obviously missing something. I can generate a sine wave output from a USB-6221 for a single frequency but the array driven steps don't work. I can see the five waveforms on the waveform chart that are specified in the array. One thing I'm not sure of is the array index function. Are there some app notes or training documents I can read to get up to speed?

[margasan]

Hello bjmcclellan

I created this example long ago you may give it a try, you just have to put the desired frequencies you wanna try in the array control and in the Actual Freq indicator you will see the current freq that is being generated. To modify the duration of each freq just incresead the wait function value in the block diagram

Regards

Mart G

[bjmcclellan]

Hi Mart,

Thanks for the example. I'll give it a try in a day or two.

Regards,

Brian