I believe the issue is with your channel configuration, especially since you mentioned that you didn't see much noise in the test panel.
Right now, you are connected in a NRSE configuration, and you need to configure your channel appropriately. To do this, you should right click the "input terminal configuration" input of the DAQmx Create Channel VI, then click Create»Constant. This will create a predefined enum constant which you can change to NRSE.
If you make this change to your LabVIEW code, I think you will get much better performance in measuring your voltage.
Is your problem solved? If so please mark the post (Whichever you think is the best solution for your query). This will help others facing same problem and looking for a solution.
well ! thanks to Abram particularly and all who helped me and answer my queries
i think i were only missing the channel configuration in software...the physical connections were all right...
when i added an enum constant it started giving me the right results...