Phase of aquisition

[Arthuruuuuuu]

Dear all,

I am measuring my experiment with DAQ assistent 9174 and two modules: NI9220 for laser transducer (displacement) and NI9237 for force.

Looking for my data generated I can see they star at the same time but they have differente aquisition rate. The mesured signal supposed to be in phase between each other and they are a little bit out of phase.

There anybody could help me with this ?

Thanks a lot, 

Arthur.

[Bob_Schor]

You need to attach (all of) the relevant VIs.  If you have several VIs in your Project, compress the folder containing them and attach the resulting .zip file.

Usually the reason two devices have a different acquisition rate is that either you set them to have a different rate or you put "slow-down" code in one or both of the loops.  But without seeing the code, we can only make a "guess" ...

Bob Schor

[orlandiisabelle]

Hello!

If you could, attach the VI of your code responsible for the acquisition. Then, we can provide a better feedback. 

Best Regards, 

[GerdW]

Hi Arthur,

the NI9237 only supports a very limited range of sample rates, see the details in its manual/datasheet!

I guess you don't use any of the supported sample rates in your VI...

[Arthuruuuuuu]

This is my VI.

My experiment deal with 20 to 30 Hz of frequency. Thats not too much i guess.

I am using continuous aquisition with 100x100 samples to read and rate.

Thanks again,

Arthur.

[GerdW]

Hi Arthur,

attach your VI instead of that huge image…

My experiment deal with 20 to 30 Hz of frequency. Thats not too much i guess.

The NI9237 starts with ~1.6kS/s sample rate. Do you use that?

Did you read the datasheet for this module?

This module does NOT support a sample rate of 10S/s!

I am using continuous aquisition with 100x100 samples to read and rate.

So you're reading 100×100=10k samples?

[Arthuruuuuuu]

Hi people, thanks for help. VI attached now.

Knight i dont understand what you mean with "This module does NOT support a sample rate of 10S/s".

I have seen many mechanics experiments for quasi-static tests measuring the force by a load cell. They operate nearly 0,1 Hz.

I dont realy understand also this samples to read and rate once i am useing continous samples for aquisition. When i increase the value of samples to read and rate i just cant measure the whole time of experiment because i get overflow on buffer.

Thanks again and sorry for my empty knolodge.

Arthur.

[RavensFan]

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@Arthuruuuuuu wrote:

Hi people, thanks for help. VI attached now.

Knight I don't understand what you mean with "This module does NOT support a sample rate of 10S/s".

Read the datasheet for your DAQ module.    Page 8 of http://www.ni.com/pdf/manuals/374186a_02.pdf

[Arthuruuuuuu]

Thanks for your answer,

but i am not familiarized with this kind of expressions:

"a master timebase"  dont know what means n...could be 1 2 3 ...or 31 but what means ?

Neither where should i introduce this equation to make then share a single time.

Thanks and sorry again

[RavensFan]

n is any of those integer numbers.

Just acquire at a higher rate!