Unable to get individual RMS readings for 4 Analog Input voltage channels from DAQ-USB-6001

[dshukla]

Hi Everyone,

I am working on a project where I am using the DAQ-USB-6001 to read Analog Voltage from 4 Analog Voltage channels.

I have attached the VI and screenshots below.

I have two problems that I am facing:-

1) I want the voltage values as well as the RMS values for each analog voltage channel.

I am getting the 4 Analog voltage values from each channel, but I am not getting any RMS value from any channel. Where am I going wrong with my VI to plot 4 RMS values?

2) Also, I wanted a way to store both the voltage values and RMS values of each analog voltage channel in the form of a TDMS file or Excell sheet for each individual trial.

Currently, I am able to store the voltage values from all 4 channels in a TDMS file but I cannot store the RMS values. 

How can I store the RMS values for each channel along with the voltage values?

I have been struggling with it for the past couple of weeks.

All the help will be much appreciated, please.

Thank You So Much!

[santo_13]

Suggestion - try to avoid using DAQ assistant - the features are limited when scaling up.

You're essentially reading the samples of the signal of interest. RMS value is not a direct measurement but rather a math operation on the raw data.

You could get the RMS value using the below function,

[dshukla]

Thank You So Much for the suggestion.

What would you suggest I use instead of DAQ Assistant in my LabVIEW VI to acquire Analog voltage signals from USB-DAQ-6001?

Could you please suggest to me some examples I could refer to, or make changes to my VI to acquire continous Analog Input voltage from 4 channels using USB-DAQ-6001?

I am new to using LabView and DAQ boards.

Thank You!

[santo_13]

You can use the DAQmx drivers to automate the DAQ instruments.

DAQ Assistant under the hood uses these DAQmx drivers to achieve your settings.

You can refer to examples under Help -> Find examples

Since you're new to LabVIEW and DAQmx, I would recommend looking at https://www.ni.com/en-us/support/documentation/supplemental/06/learn-10-functions-in-ni-daqmx-and-ha...

[dshukla]

Thank You So Much for showing me the example. It really helped. 

One more question I had was, that I would require 4 RMS blocks to log RMS values for each channel right if I use 4 Analog Voltage Channels?

How and where could I add those RMS blocks in the "Voltage-Continuous Input.vi"?

Thank You So Much!

[GerdW]

Hi dshukla,

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@dshukla wrote:

One more question I had was, that I would require 4 RMS blocks to log RMS values for each channel right if I use 4 Analog Voltage Channels?

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You are wrong: you just need one RMS function!

Use a loop to iterate over all your channels…

[dshukla]

Hi Gerd,

Thank You so much for your suggestion.

I did try to put it in the while loop, but I just got the RMS plot for one channel that is a0.

Whereas for the voltage plot, I am getting values from all 4channels as shown in the first plot in the screenshots attached below.

What changes should I make to get all 4 channels for the RMS value?

I have also attached the VI as well as the screenshots.

Thank You so much for all the help!

It really means a lot!

[santo_13 · Accepted solution]

Each element in the array after the RMS calculation corresponds to each channel/waveform.

Please note that there are 4 elements in the RMS array that corresponds to each channel.

[dshukla]

I am so sorry Santhosh but I am unable to follow your response.

Could you elaborate a bit on it?

Do I need to add an array before displaying the RMS waveform?

Thank You!

[dshukla]

Also, could you help me with how could I log the RMS values as well into the same TDMS file where it logs the voltage values?

Thank You So Much!