9223 sampling rate

[crimolvic]

Hello,

I have some questions regarding the NI 9223:

1. What type of ADC is used (e.g. delta-sigma)?

2. As far as I know, devices having delta-sigma ADC converters can sample signals at given sampling rates only. The possibilities -which are given by device-specific formulae- depend on the rate of the master timebase used. Is this also the case for the 9223? In any case, what are the possible sampling rates with the NI 9223? Considering that sampling rate is derived from the master timebase, and knowing that the timebase rate used by the 9223 is 80 MHz, the possible sampling rates could be derived by considering that the divisor must be an integer (i.e. from 1 to 80e6), is this right?

3. Does the NI 9223 includes an anti-aliasing filter? If not, how can the alisaing be handled?

Thanks in advance,

Cristián

[John_P1 · Accepted solution]

Hi Cristián,

1.  The 9223 uses a Successive Approximation Register (SAR) ADC--this is actually mentioned in the specifications.

2.  The internal sample clock must be divided down from a timebase.  On a cDAQ chassis, the available internal timebases are 80 MHz, 20 MHz, and 100 kHz.  So, any integer divisor (up to 2³²-1) of these frequencies can be generated internally (max specced rate is 1 MHz).  Alternatively, you can use an external digital signal for a sample clock or timebase if you have the appropriate digital module (to import the digital signal onto the chassis backplane), or are using an 8-slot chassis with built-in PFI lines.

3.  The 9223 does not include an anti-aliasing filter--according to the specs it has a -3dB cutoff of at least 1 MHz.  Sampling at the max rate of 1 MHz pushes your Nyquist frequency up to 500 kHz, if your source contains higher frequencies such that aliasing is a concern then you'll likely have to filter the signal externally.

Best Regards,

[sunny.garg]

Dear John Passiak,

 Could you please tell whenther I can store data directly from NI9223 to my computer through USB/Ethernet or I have to use some controller with it.

I need to sample 4 channels simultaneously at 500ks/s and I think USB communicaton is not fast enough to dump all data.

PS - I am running Ubintu in on my PC.

[Dennis_Knutson]

Please start a new thread as your question has nothing to do with this old and unrelated thread.