Data acquisition 20Ks with time stamp

[LVelozo]

Hi, Please I need help! I need to do data acquisition with 20 KHz and I would like to save these data with time stamp for each sample. I have used the myRio 1900 do it.  In my code below I have tried to read only one analog channel but after the fix my issue I will need to read two analog channel. According diagram below for each exectuion I received array with 1000 data but when I save the data in TDMS format I have only one time stamp for each exectuion.

For example the lenght date & time is 120 and the voltage is 120000.

[GerdW · Accepted solution]

Hi LVelozo,

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@LVelozo wrote:

when I save the data in TDMS format I have only one time stamp for each exectuion.

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Convert your signals to waveforms, which contain t0 and dt. Then save those waveforms to TDMS.

Then you can easily recover a timestamp for each sample…

(Does myRIO allow to read waveforms directly in the same way as DAQmx?)

[ZYOng · Accepted solution]

I don't think that myRIO has a DAQmx timing engine to store the t0. You can implement your own t0 engine. 

The inspiration is from NI CompactRIO Waveform Reference Library

[LVelozo]

Hi GerdW, first I appreciated a lot your help. Please could you share with me the example how can I recover a timestamp for each sample ? I would like to have a file with two columns one time stamp and second column with data. 

[LVelozo]

Hi ZYOng, first I appreciated a lot your help. In the example I have one column with the data, is it possible to have two collumns in the file ? I would like to have a file with two columns one time stamp and second column with data for each sample.

[JÞB · Accepted solution]

On the waveform manipulation pallet you will find a vi that takes in a waveform and returns an array of timestamps calculated from t0, dt and size of y[].  Of course, it is trivial to write yourself.  Just auto index a for loop over y, and output t0 + i * dt to an indexing output tunnel.  If you really can't find it in your heart to use a wfm instance of DAQmx read, use timestamp + i / sample rate.

[ZYOng · Accepted solution]

Use a while loop to generate an array of increasing timestamps and write it to a different channel.

[LVelozo]

Hi team, please I would like your help. I am not familiar with myRIO 1900 and I need to do data acquisition from two analog input with 20KHz and 10.000 samples with time stamp. The code below working good for one analog input I have the data record in file with time stamp, but I don`t know how to insert the second analog input. If I insert two analog input in the array connected to Smart Open.vi I had a error. 

   

[GerdW]

Hi L,

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@LVelozo wrote:

I don`t know how to insert the second analog input. If I insert two analog input in the array connected to Smart Open.vi I had a error. 

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Which error did you encounter?

[LVelozo]