Averaging scaler data

[bratvold]

I have a double precision scalar value from a DAC that represents current measured in a home wind turbine application. This value is collected from a home made circuit that has a small "noise issue".  This noise causes fluctuations in the value of plus or minus about 20% which shows up visually in the output gauge of my VI as needle shake.  The value from the DAC is read and displayed 3 times per second.  I was thinking that there must be a way to display a running average of the signal over the last N reads or N seconds which would moderate the noise and needle shake somewhat.  Tried messing with the built in RMS VI but the input data type is Array and I have double precision Scalar. I'm REALLY new to Labview and am swimming with ideas of what must surely be possible but am still working on absorbing the incredibly array of features this software has.

                            Any thoughts much appreciated.

[Eugen_Graf · Accepted solution]

You may use Point By Point VIs.

[Broken_Arrow]

I agree with Eugen that the PtByPt VI's are what you have requested. However, if you're getting "needle shake" while updating that slow - 3 times a second - then you'll be averaging in the noise rather than averaging it out. Your needle may not shake as much, but the data is still inclusive of the noise. If that's what you're after - just calming down the perceived noise on the human interface (and there's sometimes nothing wrong with that) then go forth.

Sounds like you really need a faster sample rate and a low-pass filter.

[bratvold]

Thanks Eugen! DANG that was easy! Did exactly what I was hoping and took about 60 seconds.  Cool site you linked there too. I need to spend some quality time browsing Labview help files and documentation to get up to speed.

To Broken Arrow....  Fair point. This method will include the error in the average value created. However it is just human nicety of a relatively smooth indicator I'm after not scientific precison. When I get time I'm going to make a REV II of the interface circuit to try to get the output noise eliminated in the first place.

                                          Greg Bratvold.

[Eugen_Graf]

Nice to help you 😄

The site I linked is my own, it's my signature on NI Forums.

[411051]

Hi,

I want to read vibration data from compact DAQ & display ovrall signal amplitude & FFT graph after averaging the input signal for 1 minute as vibration signal is continuously varies.  Pl. guide. I herewith attach my vi. In this vi I have not included averaging still.

[Matt.M]

Hello,

I would try taking a look at the point by point vi's linked above.  They should be the solution to your problem.