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Filtered Signal

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Hi 

I need help with the error that keeps on popping every time I run my code when I am using the filter, I am trying to measure an AC current using ACS712 current sensor. My graph has too much noise so I was trying to use the filter to at least reduce the noise, Can you please help.......

 

Please see the picture below.

Thanks a lot.

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Nope, I'm not interested in looking at a picture (unless it shows a graph of your data, showing the noise).  Please attach the VI that you are trying to use to collect and process your data.

 

Bob Schor

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In danger of stating the very obvious, but... have you checked that the filter cut-off frequencies meet the conditions described in the error message?

 

Andy

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Use of Express Nodes prevent me from any real level of surety in this guess, but I'd say that with a single value (scalar DBL type) passing into the Signals value, you have a poorly set fs value. This then outputs a Dynamic Data Type (DDT) wire with a poorly set sampling rate, and then the result becomes that the threshold values you're setting, even if they are "physically" reasonable, don't meet the criteria (as specified in the error).

 

Option 1 - Remove the express VIs, use normal thresholding/filtering VIs, and then build as necessary an array of points before trying to filter (perhaps using a For loop inside the while loop, although if possible by changing the LINX read... this might not be possible, so perhaps the loop is needed)

 

Option 2 - Keep the Express VIs but still try to form a proper array of values over time. Ensure fs is correctly set, if it is a configuration value of the Express Node.

 

Option 3 - Look for a suitable pt-by-pt filtering VI. This fits in with 1) (replace Expr. Nodes with normal VIs) but removes the necessity of an array of values over time. You'll probably need to specify fs for this option too.

 

Consider also how you want this to really work (i.e. "broad-strokes view"). You're taking the RMS value from some measurement, then filtering the output of the RMS calculation. What do you really want to have happen here? (What is the RMS value of a single measurement - not very useful. Given that, what mean value do you want? How long should your windows/blocks be? Should they be rolling or consecutive (and overlap or not?))


GCentral
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Hi 

 

Sorry please find my VI attached. I am not sure if you will be able to run it without having the components I am using. 

But You can check it below. 

 

I have also attached the picture showing the noise but that is when am using "Amp and Level" from the express signals. 

 

Thank you very much........

 

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Hi cbutcher 

 

I am new in Labview, most of the stuff you are saying I do not understand them. Sorry

 

Thanks 

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@RuruM wrote:

I am new in Labview, most of the stuff you are saying I do not understand them.


Before trying to do something a little bit complicated in LabVIEW (like acquire a signal, "filter" it, and display it), you should learn a little LabVIEW, for example by paying attention to the tutorial material shown on the first page of this Forum.  Among other things, it will teach you some of the terminology that LabVIEW uses.

 

If you are interested in "filtering", "signals", "acquiring data", you should have a little knowledge about digital representation of signals, including how A/D conversion works, and how "time" enters into things.  You mention a Filter, but show an RMS Express VI (try to learn enough LabVIEW that you never need to use an Express VI!).  I don't think of RMS as a filter ...

 

You seem to be acquiring one point at a time.  Suppose I gave you the number 3.14159 and asked you to "filter" it -- does that make sense to you?  What would you do?

 

Learn about signals, sampling, what it means to filter.  Take a course, read a book.

 

Bob Schor

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Thanks, I will do that. 

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Bob Schor


@Bob_Schor wrote:

You seem to be acquiring one point at a time.  Suppose I gave you the number 3.14159 and asked you to "filter" it -- does that make sense to you?  What would you do?

 

Bob Schor



 

pi-filter.pngA Pi Filter???  Smiley Happy

LabVIEW 8.5.1 - 2018 Pro Dev
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