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Basic measurements and Change output impedance with PXI 4461?

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I am required to build an audio testing station with NI-PXI platform.

This is my very first experience with DAQs. So i really don't know much...

The PXI 4461 card is a replacement for an old HP audio analyzer. The measurement's are quite simple:

1. generate fixed freq signal and measure AC RMS power

2. Measure THD (total harmic distortion) at fixed frequency

3. Measure SNR (signal to noise) at fixed frequency

4. Generate and measure DC signal

5.  modify Output impedance to 50Ohm and 600 Ohm.


Though I have a good feeling that tasks 1-4 are doable. I want to ask whether task 5 (changing output impedance) possible problematically?

If not any workaround?

As for tasks 1-4 is it possible doing them with out "sound an vibration" tool kit?

How helpfull will the toolkit be for the listed above (humble) tasks.

What should be my starting point learning how to handle these measurement's with Labview?


Thanks in advance

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Message 1 of 4

Hello Hazkel,


I do not believe you can adjust the impedance programmatically, but I am looking into this issue deeper.  I will have more information on it tomorrow morning.



John R.
National Instruments
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Message 2 of 4
Accepted by topic author Hazkel
12-01-2015 12:15 AM

Hi Hazkel,


The Sound and Vibration toolkit will help immensely with steps 1 through 3.  Doing these without the toolkit would require a very high level of knowledge with LabVIEW and you would likely still run into complications.  In response to step five, I have tried to adjust the output impedance and am not able to do so programmtically.  However, you can always do this in hardware by adding a shunt resistor and potentially switch between the impedances as necessary.  We have an article that discusses impedance matching and how to configure a circuit to adjust the impedance if you are interested:


Impedance and Impedance Matching



I recommend starting with examples that we have already been built in LabVIEW to become familiar with the concepts.  You can find these by clicking Help-> Find Examples -> search, and then searching for your application. Please let me know if you do have any other questions.



John R.
National Instruments
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Message 3 of 4

many many thanks. You helped a lot!

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