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Problems with proper sample rate


So I asked You about my parallel data acquisition problem about a month ago, thankfully after adding second daq the code compiled with no problem.

Since then I'm stuck with sensors sampling rate. I use 2 -K type (NiCr-NiAl) single thermocouples, and 4 pressure gauges for measurement. Also I'm building tachometer which will measure up to 120 000 rpm (hope so -small jet engine).

Thermo and pressure are on one Daq,and when I set number of samples and rate two problems occur- buffor overlfow so it crashes,and when I lower number of samples-it says that rate is too big. It works good until low values like 20 samples per second(it was when last time I tried home-built tachometer and simulating other signals ,due to closed university with all the stuff.At lab with all the senors I edned up only with buffor overflow, couldnt fixing it).Could You tell me what is the problem? I'm not experienced,maybe such a low values are enough for not sinusoidal signal,as I only desire value at the moment.

Sorry for bothering You, but my professors don't really know what is the issue, plus due to covid I have acces to lab once for 2 weeks, so I want to be prepared the best I can.

Thank You.

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Message 1 of 4

You should attach your latest VI's.


If you are getting buffer overflows, you probably don't have you sample rates and the number of samples to read balanced right between DAQmx tasks.


It is also possible that the DAQmx rate you are setting on a particular task is being coerced to a different value.  I know that can happen for temperature tasks.  Be sure to comment what DAQ module model numbers you are using for the various inputs.

Message 2 of 4

So here is my VI, it's not really sophisticated, thermo and pressure are calibrated lineary,so I just made it simple analog input.

I use two NI 6001 usb.

So what rate and number of samples would be optimal in such situation?

Thank You

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Message 3 of 4

I see you are using NXG.  I don't have that installed, and most people on the forums aren't using it. It might take awhile before someone who uses it sees this thread and responds.

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Message 4 of 4