Digital AI Filtering

The NI 4302, 4303, 4304, 4305, 4339, 4480, and 4481 modules have a user-configurable lowpass filter for their analog input channels. This filtering is implemented with a digital elliptical filter. It is configured independently of the tracking anti-aliasing filter. It may be helpful when measuring in an environment with excessive high frequency noise below the anti-aliasing filter's cutoff.

When sampling in hardware-timed single point mode, the filter is always enabled. You can set or query its cutoff frequency using the AI.DigFltr.Lowpass.CutoffFreq attribute/property. If your application does not require this additional filtering, leave this property set to its default value. This will configure the widest bandwidth filter possible.

Digital AI filtering for hardware-timed single point mode is supported on the following modules:

Modules Default Cutoff Frequency Support Cutoff Frequencies
PXIe-4302, 4303, 4304, 4305 2 kHz 100 Hz, 200 Hz, 500 Hz, 1 kHz, 2 kHz, 3 kHz
PXIe-4339 2 kHz 200 Hz, 500 Hz, 1 kHz, 2 kHz , 3 kHz

When using other sampling modes, the filter is optional. This filter can be enabled by using the AI.DigFltr.Enable attribute/property, and you can set or query its cutoff frequency using the AI.DigFltr.Lowpass.CutoffFreq attribute/property.

The following modules support digital AI filtering in other sampling modes:

Modules Default Cutoff Frequency Support Cutoff Frequencies
PXIe-4302, 4303, 4304, 4305 None 2 Hz, 20 Hz, 200 Hz, 1 kHz, 2 kHz, none
PXIe-4480, 4481 2 MHz 2 MHz, user-defined
Note User-defined cutoff frequencies for the 4480 and 4481 are supported only for sample rates greater than 1.25 MHz.