How to change input mode for 7831R?

[ChrisFTC]

Hi,

I was wondering how I can change the input mode (DIFF, RSE, NRSE) of the analog inputs for the PXI 7831R card.

Thanks,

Chris

[Prashanth]

Hi Chris,

The links below contain the information you are looking for.

• Analog Input Mode Configuration of FPGA Board in LV 7.1: http://digital.ni.com/public.nsf/websearch/A1E383B68B8BE6BA86256E6A007BA654?OpenDocument
Input Mode Configuration of FPGA Board in LV 7.0: <http://digital.ni.com/public.nsf/websearch/44DCAF488ACABCA586256E1A005E8F3D?OpenDocument>

Have a great weekend!

Regards,
Prashanth

[ChrisFTC]

Hi Prashanth,

Great! Thanks alot for your help.

Chris

[ChrisFTC]

I have another problem with this:

I set the Input Mode to NRSE and flash it but nothing seems to change. I get the same measurement results as in DIFF mode (Signal is still hooked up to A+ and A-). Shouldnt the differential Mode be disabled? Whenever I start the FPGA utility to configure the Inputs it says "Differential". Should it automatically update to the current state or does it always say "Differential"? How can I check which state the Inputs are currently in?

Thanks,

Chris

[Prashanth]

Hey Chris,

Differential mode uses 2 AI channels for acquiring measurements from one source and the voltage is measure by taking the difference in voltages at Ch+ and Ch-. Differential mode is useful because it minimizes the noise in the environment. Unlike differential mode, NRSE mode requires you to connect the negative end of all your data sources to the AISENSE terminal and the positive end to AI channel. So, NRSE and Differential modes will provide the same functionality for a single channel but will differ for more that one channel acquisition.

By using differential mode were you expecting to increase accuracy for your acquisition? If there is not much noise in the environment around, then the values you acquire from these two different modes could be very close to each other that they seem the same.

When the acquisition modes are set from the embedded project window, the selected mode is written to the nonvolatile memory of the FPGA hardware and is stored there. If you open the embedded project window again, the selection will show differential mode as default and does not hold on to the previously selected mode (in the project window). However, since the mode information is stored in the actual hardware,the mode is not updated till it is explicitly specified to update the actual hardware with the mode information.If in doubt of the mode selected, I would just reset the mode to the desired value and this should only take a few seconds.Hope this helps!

Regards,
Prashanth

[Jirav_Fadia]

Hi Prashanth,

Can you please describe the procdure to change analog input mode in NI 7831R

Above attached link does not work...

Thanks in advance