Matlab code for NI 4472

[VGR]

Hi,

Can anyone help me with Matlab code to stream data from NI 4472 board to disk. I am using an IEPE microphone, single board, 8 channels.

Reju 

[KateB]

You need to have Matlab's Data Acquisition Toolbox as shown in http://www.mathworks.com/products/daq/supportedio14005.html
An example should available with toolbox.

[VGR]

Yes, I have the Matlab data acquisition toolbox. The device I can see, but while reading I am getting only some noise.

[KateB]

What is reading result, if you read it using LabVIEW?

I ask this to make sure that problem comes from software or hardware.

[VGR]

Using LabVIEW I recorded some data, but there is some problem of noise. (this problem I posted under the subject “Issue of Sound measurement System using PXI-4472 DSA module”  in this discussion group.

I used the example program provided with LabVIEW (Hardware Input and Output\DAQmx\Analog Measurements\Sound Pressure\Cont Acq snd Pressure Samples-Int Clk.vi). Even in a quiet lab environment the noise level is very high.

Two screen shoots are also attached along with this. Fig1 is in the absence of any signal, i.e., noise only. It can be seen that the noise level is very high. Fig2 is for the case where the word ‘Hello’ is recorded. The recording was in a quite lab environment.  The microphone used was GRAS-40PL  IEPE microphone. I tried with IEPE microphone from other manufacturer also. The same noise is present in all the channels. 
  
Another problem is while using all the 8 channels at higher sampling frequency, say 44.1kHz, it is giving time out error. How this problem can be solved? The program which I used to record the data is also attached along with this.

[preston_johnson]

In your VI, I would change the read size in the data acquisition assistant block.  For example, make the read 8k instead of 2k while sampling at 16kHz.  In the background, this will have the DAQmx driver create a larger block of memory for the buffer and it should reduce the errors. 

In your pdf document, you have 200m PA of "noise" pressure that is on the order of 10 hz.  This is low noise pressure that is likely coming from the HVAC system.  You may not hear this noise, yet the action of the fans in the HVAC system are slightly changing the pressure in the room as they rotate, and this impacts the measurement.  You can use Subset FFT from the NI Sound and Vibration Measurement Suite for example to focus spectral analysis on those frequencies of interest. 

When using MatLab, I would use the DAQmx NI supplied driver for the 4472.  http://zone.ni.com/devzone/cda/tut/p/id/3005 

This document introduces NI-DAQmx Tools for data acquisition with The Mathworks, Inc. MATLAB®¹ evaluation software that allows you to work with National Instruments data acquisition hardware from MATLAB® software. As we’ll see, this evaluation software offers major advantages over The MathWorks®, Inc.’s Data Acquisition Toolbox for MATLAB® software.