LabVIEW
signal filtering
Solved!
I totally agree with GerdW. Filters can be tricky -- not being an Engineer, I always get Low-Pass and Low-Cut confused (it doesn't help that for LabVIEW's Low-Pass Filter, the Filter Frequency is wired to the low cutoff freq).
What you need to do is learn about LabVIEW Filters. While you are at it, you might learn a bit about Waveforms, the LabVIEW Data Type for sampled data.
I recommend building a simple simulation that creates, say, a 10 Hz Sinusoid and adds to it a noisy Gaussian. The Waveform Palette has VIs to generate these signals. Once you have the two Waveforms, pull the sampled data (called "Y") out and add them to make a "noisy sinusoid". Now filter it, using the Filters in the Waveform Palette (they have names similar to the Point-by-Point filters you may eventually want to use). Now plot the filtered waveform and the unfiltered, and see how it works.
This Snippet (I'll attach the LabVIEW 2017 code, as well) does just this. The Cluster on the left says "Sample at 1000 Hz and take 100 points/sample"). By design, these functions are designed to work properly within a Loop. The 100-ms Wait slows the function generation down to 10 Hz so you can see what's happening. You can see I'm using a Butterworth Filter, LowPass, with a corner frequency of 20 Hz.
Experiment a bit with this code. Put your own filter in there. Change the Input signal. Add more (or less) noise. Once you think you know what you are doing, try it with real data. But, please, do NOT use the DAQ Assistant, and definitely do NOT use the Dynamic Data Wire -- it will only cause problems and confusion for you.Filter Example, FP Chart
Bob Schor
