DAQ systems for hydrophone array, been using PXI-4472

[Walsh]

I am wondering what makes the PXI-4472, and now the PXIe-4492 better for acoustic measurements over other systems. We have been using the PXI system for many years and now are looking to build a small system for deep sea hydrophone arrays, smaller then a PXI chassis. Are these the best boards to use and why? Can the X-series produce the same quality? Are there other boards I'm unaware of for systems like this?

I require up to 16 inputs and would like to sample all channels at least 102.4 kS/s

[Travis-E]

Hello Walsh,

There are a couple main reasons why a Dynamic Signal Acquisition (DSA) board is a better option than an X-Series card. The DSA family of boards have a 24 bit analog to digital converter versus the 16 bit ADCs of the X-Series cards. Also, DSA boards use a Delta Sigma ADC which is specially designed for our more high end cards. Here is a link that discusses more about the Delta Sigma ADC: 

http://www.ni.com/white-paper/11342/en

DSA cards usually come with the functionality to provide excitation current for IEPE devices. X series cards can take the same measurements but they will not be as accurate and they do not provide excitation. I hope this is helpful.

Regards,

[Kurt_Veggeberg]

As mentioned, the dynamic signal acquisition modules offer 24 bit resolution with built-in anti-aliasing filters with very sharp cut-offs.   The 24 bit resolution gives you a dynamic range of around 113 dB which typically is a better match for the dynamic range of the hydrophones you might use.    Sampling at 102.4 kS/s, the NI 449X modules will give you an alias-free bandwith of 47 kHz.    The NI 449X modules can sample at up to 204.8 kS/s.  These modules are widely used for naval microphone arrays.    

Don't overlook the capabilities of the platform for feature extraction.   The Signal Processing Toolkit has some excellent tools for wavelet and filter-bank design for short-duration signal characterization, noise reduction and detrending.  

Sometimes the object of your interest (for example, an animal) does not have a reference signal of the fundamental frequency. You can use order analysis tools in the Sount and Vibration Measurement Suite to create a fundamental frequency profile interactively and eliminate the background noise of the ocean. After we extract the primary harmonics, add them together, and play them back, you can hear a clean signal.. 

Here is an example where these were used to denoise a whale call signal.