Initialize the Smoothing Filter

[ScottR22]

I'm using the "Filter" vi off the Waveform Conditioning Palette to smooth some data being collected from a fairly noisy sensor. I use it in a program that plots the Frequency Response of electromechanical actuator, and if I run it a second time with a new data set, the measurement gets distorted as if the filter isn't getting initialized, but if I stop the program and restart it works perfectly.

The vi doesn't offer any option to "initialize" it, and I if I try to build the function discretely, I get vastly different results.

Any suggestions on how I can initialize it without restarting the program?

[JÞB]

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@ScottR22 wrote:

I'm using the "Filter" vi off the Waveform Conditioning Palette to smooth some data being collected from a fairly noisy sensor. I use it in a program that plots the Frequency Response of electromechanical actuator, and if I run it a second time with a new data set, the measurement gets distorted as if the filter isn't getting initialized, but if I stop the program and restart it works perfectly.

The vi doesn't offer any option to "initialize" it, and I if I try to build the function discretely, I get vastly different results.

Any suggestions on how I can initialize it without restarting the program?

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Let us see some code!

Generally,  filter VIs do have a "reset? Input that is an "Optional" terminal default to False.  Those Optional terminals are not normally shown in the context help window!  There is a tiny icon on the lower left of the context help window that toggles the view of Optional input terminals!  😀

[ScottR22]

It's an Express vi, there are no additional "Optional" terminals.

[GerdW · Accepted solution]

Hi Scott,

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@ScottR22 wrote:

It's an Express vi, there are no additional "Optional" terminals.

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So the simple solution is: don't use the ExpressVI, but use the filter functions in the signal processing palette…

[ScottR22]

Agree, but as I stated when I try to implement a moving average filter, I get very different results, and i would like to know what exactly is being done under the hood of this "canned" vi to make that the case?

[ScottR22]

I found my mistake, this solution works.

[GerdW]

Hi Scott,

another option to implement a moving average:

[ScottR22]

That's actually the way I first tried to implement the moving filter, but I didn't have the for loop, I just sent blocks of the waveform data into the mean function as an array, the problem is it decimated the waveform so and I forgot to update my X-Axis accordingly. Using the discrete functions you suggested from the Signal Processing palette produced the exact same results as the Express vi without the Initialization issue, so theres a bug in the Express vi for sure.

Thanks for you assistance.

[GerdW]

Hi Scott,

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@ScottR22 wrote:

That's actually the way I first tried to implement the moving filter, but I didn't have the for loop, I just sent blocks of the waveform data into the mean function as an array, the problem is it decimated the waveform…

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That's why I depicted the Pt-By-Pt_Mean function: it doesn't decimate the incoming data…

[ScottR22]

Appreciate it.