Finding the right filter!

[glskinner84]

Hey guys, I'm looking to filter an accelerometer signal with Labview, to clean up the noise a bit. My frequency range is 10-120hz or so and my voltage output ranges from 20mv-9v or so. The Signal looks good at 9v, obviously but I'm concerned about the lower voltages.

My current vi is using a zero phase filter which then is averaged out and sent to the graph. My question is...can I do  this better? I'm still getting some noise.

[johnsold]

When selecting or designing a filter you should start with the characteristics of both the signal and the noise. You indicated a frequency range for the signal but did not specify the waveform or the harmonic content. You said nothing about the noise.  Is it random or is it the result of some interfering signal, such as power line frequency interference? What is the amplitude range of the noise? Does the desired signal consist primarily of a single frequency and its harmonics or is it more complicated? Do you know the signal frequency at each instant (for example from a driving source)?

If possible it is better to prevent the noise or interference from getting into the data than to try to filter it out later.

We do not have your hardware so please put an indicator on the output of DAQmx Read.vi and run the until some typical data is in the indicator. Stop the VI and select Make Current Value Default from the Edit Menu. Then save and post that VI. That way we can see your signal and noise and test other options.

I have worked with filters for forty years and have never used the zero phase filter.  It looks like you are not actually definining a filter since you do have the filter coefficients subVI.

Lynn