How to reduce the noise from acquired data?

[Bombbooo]

Hello,

I would like to ask about how to reduce the noise of the data acquired from DAQ. My programs mainly measure temperature, pressure and flow rate. The acquired values are fluctuating all the time which should be constant. I think it is the noise from the signal from my USB. Are there any block functions to handle this issue? And where to insert it? Thank you in advance!!

[altenbach]

Could you crop your picture so we can actually see it? Currently it is over 2500pixels wide, containing mostly white space?

[Bombbooo]

ok I would better attach my VI. Thank you in advance

[AndyClegg]

I've just posted a reply about filtering here - https://forums.ni.com/t5/LabVIEW/Better-Filter-VI/td-p/2065446

Might be useful here as well.

[Marco_Brauner]

Hi Bombbooo,

for analyzing noise-related issues, a good approach is to compare the measurements with the results you get

from a trusted example VI or test-application for your measurement device.

If you don´t see the noise with those but with your VI you can dig deeper into the code to debug.

Did you compare your results with the results of a shipping example VI or test-app?

regards

Marco Brauner NIG

[Ray.R]

Before software is written for a data acquisition, one must make sure that the signal being acquired is actually that which one wants to acquire.  Most of the time, this is solved by signal conditioning.  There are many things to consider:  The length of the wire carrying the voltage to the DAQ card, shielding, amplification of the signal to a range suitable for the DAQ, configuring the DAQ to the proper voltage range, filtering, and so on.

I have not looked at your code and would not consider the code until I know that the DAQ is getting the cleanest signal from the transducer.  The issue first needs to be fixed at the source, because no wizzardry will make that better.  Once a good / clean signal is acquired by the DAQ (which could be confirmed by an oscilloscope), if there is undesired waveforms in the data (that did not show up on the scope), then it is time to look at the software.

[Bombbooo]

@ Hans Aplast

Yes i already compare the signal between the data acquisition VI of the test bench (From the company) and my own VI (which I imported the test bench VI to connect with my own program). The signal fluctuations are in similar level. It is not the problem with my program. I think it is coming from the signal generation of the USB ports

[Marco_Brauner]

Ok, that´s what I was expecting 😉 

Please check out the tutorial about field wiring of signals which is about preventing noise-injection. 

https://www.ni.com/en/shop/data-acquisition/measurement-fundamentals/field-wiring-and-noise-consider...

Marco Brauner NIG