Signal Filtering

[LarsUlrich]

I have a pretty basic need for the filtering capabilities of LabVIEW.  We measure accelerometer data over a period of time and filter out all frequenicies that are above 500 Hz.  

Essentially, I need a program that reads from a 2 column, tab-delineated text file, puts a 500 Hz lo-pass filter on the data, and saves to a new file.

Below is a very simple block diagram, along with the filter settings, and the error I receive, when I attempt to run it with data obtained from a previous test that was not filtered.

[Dennis_Knutson]

Your 2D array has no timing information. Simply converting to the evil dynamic type does not add the necessary dt. The function is defaulting to a dt of 1 second. Did you actually save timing in the file?

[LarsUlrich]

The file is 2 columns, G forces and time.

I thought maybe it wasn't working because the .vi might only take a live signal, rather than a stored data file.  Not sure about that though.

[Dennis_Knutson]

The source of the data is irrelevant. What you have to do is format the data correctly. From the column with the time information, get the t0 and dt and set that with the build waveform function. Without that, you would have to manually provide dt to one of the lower level filter functions.

[LarsUlrich · Accepted solution]

Well, I am making progress, thanks for the help.  Still getting an error though.

[Dennis_Knutson]

Sorry, since you did not attach the VI or the file, impossible to say what else might be wrong. Look at the data array and the express filter settings.

[LarsUlrich]

Attached are the .vi and data file

[Dennis_Knutson]

According to your picture, you are extracting the time column. Set the column index to 1.

[LarsUlrich]

You are correct, but I still get the error message.

[Dennis_Knutson]

I am now away from a pc with LabVIEW. Perhaps someone else can look at the VI. As I said, look at the express configuration.