Analog Input >> General Properties >> Digitizer/ADC >> Dither >> Enable

NI-DAQmx C Properties

Analog Input >> General Properties >> Digitizer/ADC >> Dither >> Enable

Data Type: bool32
Description: Specifies whether to enable dithering. Dithering adds Gaussian noise to the input signal. You can use dithering to achieve higher resolution measurements by over sampling the input signal and averaging the results.

You can get/set/reset this property using:
  DAQmxGetAIDitherEnable
  DAQmxSetAIDitherEnable
  DAQmxResetAIDitherEnable