Maruthi;
The problem might be related to a wrong choice of the input gain of the DAQ board. Since your data input voltage range is quite small, you need to apply a gain on the DAQ board so the input signal is amplified to best fit the DAQ board input range of 0-10V.
In Labview you can change the input level parameters at the AI Config.VI to best characterize the voltage range of the input signal.
After that done, run the VI and don't do any unit conversion. Acquire and show the voltage level that the sensor is delivering, and see if that voltage value make sense.
If it does, you can configure a Virtual Channel in MAX to convert the voltage reading to the desired physical unit, and then use the Virtual Channel created as the input channel in Labview.
Hope this helps.
Filipe A.
Applications Engineer
National Instruments