DAQ Assistant and Exel

[o225oe]

Hello.... I am using DAQ Assistant to acquire acceleration data and using Write to Measurement File to save the data as an Excel file. Despite adjusting the "samples to read" and "rate" values, the time intervals in the Excel file (first column) appear to be 0.001 seconds, and there are many overlapping entries. I would like to resolve this issue..... 

[NIquist]

Sorry, but showing us a picture of Express VIs is of no use.  We need the actual code to see how they're configured... 

And then tell you why you should dump them and code in real LabVIEW. 😋

[Bob_Schor]

Please attach the LabVIEW code (preferably the entire Project, perhaps with the Project Folder compressed to a ZIP file by right-clicking the Folder, choosing "Send to:", "Compressed (.zip) Folder").  Many of the more-experienced LabVIEW users (myself, included) are not running the "latest" version of LabVIEW, so you need to do a "Save for Previous" and specify LabVIEW 2019 or 2021 (which seem to be the most popular suggestions on the Forum).

You should learn DAQmx (which isn't difficult to do).  I recommend "Learn 10 Functions in NI-DAQmx and Handle 80% of your Data Acquisition Applications" (I've recommended this so many times on the Forum that I've memorized the name to give to your Favorite Search Engine).  Skip the first entry, which described the Dreaded DAQ Assistant, and read the next few sections showing how easy/powerful DAQmx can be.

Bob Schor

[o225oe]

Hello!

I am trying to measure data using the DAQ Assistant, and I would like to know why Samples to Read and Rate are set separately, as well as the reasons for error 200279. Also, I am curious if these reasons are related to the number of loop executions or their speed.

And I want to What is the FIFO, How to operate in softrware...

[o225oe]

Sorry...! I can't spend you file now....

But I appreciate your response!

[o225oe]

Hello!

I am trying to measure data using the DAQ Assistant, and I would like to know why Samples to Read and Rate are set separately, as well as the reasons for error 200279. Also, I am curious if these reasons are related to the number of loop executions or their speed.

And I want to What is the FIFO, How to operate in softrware...

[GerdW]

Hi o,

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@o225oe wrote:

I am trying to measure data using the DAQ Assistant, and I would like to know why Samples to Read and Rate are set separately,

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Use DAQmx functions as mentioned before!

You set samplerate and #samples separately because they describe two independent parameters of the DAQ reading!

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@o225oe wrote:

as well as the reasons for error 200279. Also, I am curious if these reasons are related to the number of loop executions or their speed.

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Your error most probably is -200279 (the sign is important!): you read too less samples for your high samplerate!

Recommendation: set #samples to about 1/10 of the samplerate...

The "number of loop executions" (aka loop iterations) does (or should) not influence your DAQ reading.

The speed of those iterations should be defined by the DAQmxRead functions without any additional wait function!

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@o225oe wrote:

And I want to What is the FIFO, How to operate in softrware...

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What are you talking about?

Mind to rephrase this sentence?

[o225oe]

Thanks to your respond!

I am a non-major who just started learning LabVIEW, so I need an appropriate example. Is that possible? The part I don't understand is if the Rate is 1000Hz and Samples to Read is 100, does that mean 1000 samples are collected per second, and therefore 100 samples are read every 0.1 seconds?

And for the last sentence, it's because of my poor English skills. I'm sorry. While researching the -200279 error, I gathered information about buffer size and FIFO, but as a non-major, I couldn't understand what it means. Please help me.

[GerdW]

Hi o,

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@o225oe wrote:

The part I don't understand is if the Rate is 1000Hz and Samples to Read is 100, does that mean 1000 samples are collected per second, and therefore 100 samples are read every 0.1 seconds?

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• The sample rate is given as "Hz" or "samples per second"! A sample rate of 1000S/s means exactly what it is: 1000 samples per second...
• What is the expected acquisition time when you request 100 samples with a sample rate of 1000S/s? This is very basic math, using the relation of "time = #samples / samplerate"...

(Your example is correct.)

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@o225oe wrote:

While researching the -200279 error, I gathered information about buffer size and FIFO, but as a non-major, I couldn't understand what it means. Please help me.

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The main source of this error is: you do other things in the loop that take more time than needed for DAQmxRead, so the samples in the DAQmx-internal buffer are collected until the buffer overflows.

As I said before: just DAQmxRead should define the loop iteration rate, nothing else!