7831R Analog Input Noise Problems

Hi,
I am running a data logging application which samples the analog inputs of my 7831R FPGA card with a sample rate of 10KHz. I am interested in how noisy the PXI system itself is, so I shorten AI0+ and AI0- together, hook both of them up to A0GND through a 10K resistor (all done in the SCB-68 breakout box which is connected to the FPGA card through a SH68-C68-S cable) and log data from the analog input.
The data log shows about 12 counts of noise in the system. That's about 3.5 bit. Is there any way I can reduce the noise?
Thanks,
Chris

Hi Pete,
You are right in saying that the 7831R boards should acquire data much faster than 10KHz. Infact you can take a look at the actual specs from the data sheet http://sine.ni.com/nips/cds/view/p/lang/en/nid/14757 as well as the product manual. However, I am concerned that you may be measuring the rate of acquisition on the RT VI (or any host vi) you are running as opposed measuring it in the FPGA VI.
Your time critical loop may be running at 228 ticks of the 40 MHz clock but the data is buffered (at that rate) and has to be then transferred to the communication loop which then sends the data to the host vi (which may be your RT vi). Hence, the rate at which host VI receives the data will be much slower than the FPGA VI is acquiring data.
Hope this helps!
Prashanth

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