Max. Sampling Rate NI-9205

[KoBe]

Hi people,

I'm using my 9205 together with a cRIO-9073 and Labview 8.6.1 RT+FPGA Module.

I have two similar projects, both should sample with 10KHz a different number of RSE inputs reading calibrated values with the FPGA interface (not scan engine).

One project needs 10 inputs, the other one needs 14 inputs. With 10 inputs everything works fine. Supposing an overall sampling rate of 250KHz I can sample 10 channels with 10KHz each (250KHz/10=25KHz >= 10KHz). Also 125KHz would be enough (125KHz/10=12,5KHz >= 10KHz).

Unfortunately the maximum sampling rate with 14 inputs seems to be around 8,9 KHz only!!! That would mean the NI-9205 is sampling with only 125KHz instead of 250KHz also in RSE mode. (125KHz/14=8,9KHz < 10KHz!!!!!) Why that? How can I reach the 250KHz for all 32 channels described as maximum sampling rate on the official data sheet of the NI-9205?

Can it be that the NI-9205 uses 2 16-channel ADCs with each 125KHz? That would mean I have to measure at maximum 12 channels with a single multipled ADC to maintain a sampling rate >=10KHz per channel. Any information about that?

If anyone could give me further information on the maximum sampling rate in different operating modes (RSE, NRSE, Differential) with a different number of channels I would be very happy and grateful.

Thanks

Bye

KoBe

[Tim_S]

I'm using my 9205 together with a cRIO-9073 and Labview 8.6.1 RT+FPGA Module.

[snip]

There is one A/D converter multiplexed. I don't see a multi-channel rate, so the multichannel and single channel rate should both be 250 kHz aggregate. You should be able to get 17+ kHz with 14 channels. The hardware can handle the DAQ you are looking for, so I'd recommend you look at the way you're moving the data about.

Tim