DAQ program

[Snow_In_Tehran]

I'm trying to write a program that runs in a loop and samples 11 different channels on a NI USB DAQ 6343 device continuously. The first 10 channels are simple DC measurements, the remaining channel is an AC voltage signal, whose frequency I want to record. All of this data I will be writing to a .csv file at the end. I have attached my code and I'm working with the DAQ.mx drivers. 

The question I have is, how do I measure and AC signal with the USB DAQ? I tried to configure analog input channel # 19 for "frequency, voltage" and then do a "read", howeever, it is telling me that the channel does not support that type of measurement. This AC signal is going through a BNC cable, and then to two banana adapters.

Attached is my code, written in LabVIEW 2013.   Here is a screen shot .

[Dennis_Knutson · Accepted solution]

You just include that channel in the ai voltage channel list that you already have. It's part of the same task. Change to n samples and specify a rate and number of samples to read. Since your dc channels would consist of multiple readings now, you could do something like take the mean of those.

[Snow_In_Tehran]

Thanks for your reply. I see what you're saying in terms of including the channel in the original list, since its the same task. However, how do I record the freqnecy. Don't I need to designate that channel alone (using virtual channel) as a voltage-frequency measurement?

If I just do "N channel, N sample read" for all 11 channels, I will get the voltage levels for those channels, but how will I know the frequency of that last channel (the AC signal)?

Should I use some other vi's to look at that channel after its been read to calculate the freqnecy of that input? 

[crossrulz]

Look for the Signal Processing->Waveform Measure->Extract Single Tone Information.vi.  It performs an FFT and gives you the main frequency of the waveform.

[Snow_In_Tehran]

Ok thanks, this is a real help for getting the frequency data. However, the only problem is that by going from 1 sample read to N samples, the output data out of the 'read' vi is in waveform mode. This creates problems for my other processes becuase I wanted to scale the DC voltages by constants and then write the modified values to a .csv file. I can't do those operations when my data is in waveform form.

i tried to undundle the waveform data thinking that it is a cluster, but that doesn' work. Any suggestions?

[John_P1]

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@Snow_In_Tehran wrote:

i tried to undundle the waveform data thinking that it is a cluster, but that doesn' work. Any suggestions?

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The function you're looking for is called Get Waveform Components.

Best Regards,

[Dennis_Knutson]

Please use single Index Array and I already told you what to do if you wanted a scalar for the dc readings.

[Snow_In_Tehran]

Thanks, these were all great answers and have helped me to solve the problem.

[Snow_In_Tehran]

Ok this has worked great. My only problem is, as you mentioned, now I have many more samples and I end up with a csv file with a huge number of rows and columns.

originally it was just 11 columns corresponding to my 11 channels. What kind of averaging operation can I employ to make the output more readable like it was before? 

Thanks

[John_P1]

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@Dennis_Knutson wrote:
Since your dc channels would consist of multiple readings now, you could do something like take the mean of those.

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There is a Mean function that does exactly what Dennis suggested.

Best Regards,