setting PXI 4472 anti-alias filter

[Panthera395]

Please excuse what is probably a very stupid question.  I am new to using the PXI DSAs

On a PXI-4472 DSA (as run by a PXI-8196 controller running LV 8.2) how do you programmatically set the cutoff frequency for the anti-aliasing filter?  Can you even do this?  I tried using the AI.Lowpass.CuttoffFreq property to set it, but it just returns error -200452 and says that "Specified property is not supported by the device or is not applicable to the task."

Thanks!!

[devchander]

As you have already realised, you cannot set the cutoff freq of this filter.

The 4472 anti alias filters automatically adjust their cutoff frequency to remove any frequency components above half the programmed sampling rate

However, you can programatically enable or disable it using 'AI.EnhancedAliasRejectionEnable' property

This property is disabled by default for your PXI 4472

[Neil_S.]

Panthera395,
devchandler is correct the cutoff frequency is automatically set based on the sampling rate.  The only way to modify the cutoff frequency is to either disable to filter, or change your sampling rate.  For more information take a look at the NI Dynamic Signal Acquisition Help:

http://digital.ni.com/manuals.nsf/websearch/FCD835105CD3A20E86257130005DA240

The section on the Anti-Alias Filters explains the behavior of the anti-aliasing filters in more detail.  Let us know if you have any additional questions.  Good luck with your application.

Regards,

Neil S.
Applications Engineer
National Instruments

Message Edited by Neil S. on 09-14-2006 12:39 PM