Analog Input >> General Properties >> Filter >> Analog Lowpass >> Enable

NI-DAQmx C Properties

Analog Input >> General Properties >> Filter >> Analog Lowpass >> Enable

Data Type: bool32
Description: Specifies whether to enable the lowpass filter of the channel.

You can get/set/reset this property using:
  DAQmxGetAILowpassEnable
  DAQmxSetAILowpassEnable
  DAQmxResetAILowpassEnable