Where can I find the amplitude and phase frequency response when the AC coupling is set on the 4472

[crimolvic]

My friends,

  I need to know the amplitude atenuation but most important, the phase distortion introduced on the low frequency components of the signals when the AC coupling is setted (i.e. when the high pass filter is connected) on the 4472 and 4472B DAQBoard.

  I can construct the amplitude frequency response by generating and aquiring a sine waveform of a knew amplitude. But I cannot construct the phase distortion introduced by the circuitry. 

  However, I assume that this crucial information should be available in the DAQ Manual or  in the website of NI, but untill now I haven´t found it.

Thankning in advance,

crimolvic from Chile

[Travis_W]

crimolvic,

Here are the Specifications and Datasheet for the 4472.  They indicate a phase non-linearity of less than 0.5 degrees across all frequencies.

For information on how this varies with frequency, see the attached spreadsheet.  This response was the result of testing on a single 4472.  Although this is classified as a "typical" response, it is not gauranteed.

Have a great, day!

Travis

[crimolvic]

Dear Travis,

  Could you please give the details of the test that you performed in order to get this phase-frequency response? did you use a sine waveform with a pulse trigger?

Greetings,

crimolvic

[Travis_W]

Crimolvic,

I did not perform the test myself.  Here are the notes I have about what was done:

A precise function generator was used to generate a square wave at 500 Hz. The square wave is composed of sine components at frequencies n, 3n, 5n, 7n, etc. For a perfect square signal, the phase relationships between these components is known in to be zero. Assuming the actual phase relationship really is zero (a reasonable assumption), we then calculate the phases of each component as measured by the 4472 and make a linear fit. The values on the graph at each frequency show the absolute value of deviation from that linear fit.

Have a great day!

Regards,
Travis