resolution

[NAUSHICA]

Data sheet of PXI-6289 says, it has atleast 14 bit effective resolution when it is operated at 500kS/s.
(Pls refer "http://www.ni.com/pdf/manuals/371292d.pdf" Table 1
+-4LSB for Settling time of 2us @ +-10V / +-5V ranges )
Is this correct even when you connect SCXI-1125 in parallel mode to PXI-6289?

I know that in MUXing mode, SCXI-1125 will have only 13-bit resolution for 333kS/s scan rate.
But the reason I think is because due to the uncertainity of the multiplexing timer.
(SCXI-1125 manual, page A-4)


So will I get more resolution in parallel mode with these two modules?
If so, I would like to know whether if this setup works in 125kS/s rate,
will I get 17bits of resolution for my signals?

Rg.

Naushad

[Kurt_NISalesEngineer]

Hi,

Thanks for posting your query on the NI discussion forums.

The multiplexer that is used in the SCXI system needs additional settling time to achieve something like 16 bits of resolution. An SCXI system that is scanning at 333 kS/s will achieve about 14.5 bits of resolution with a 16-bit DAQ device.

To fully understand this solution, it is important to note one of the fundamental differences between Traditional NI-DAQ and DAQmx. In Traditional NI-DAQ, each channel is scanned as closely as possible to each other so that the operation is as simultaneous as possible. In DAQmx, the scan of each channel is evenly spaced over the course of the total scan. This provides for longer settling times which can reduce noise in a DAQ system and provide more accurate readings.

Also you are correct in acknowledging that when multiplexing, you cannot expect to get the same performance that you would get in parallel mode.

You might find the information at the following KB link useful:

Problem: How do I determine the maximum scan rate with the modules and DAQ board I have? Is it based on the module with the slowest scan rate? Or is there a simple equation I can use? http://digital.ni.com/public.nsf/websearch/410A70C25A4D12B486256A1E0070BDAE?OpenDocument

I hope this helps!

All the best,

Kurt

NIUK Applications Engineer