NI4461 PCI card- DAC output abnormality

[anandu]

Hello,

         I am using NI4461 PCI Card for a frequency response analyser application. Otherthan that I am having a specific profile waveform to be generated using a DAC card.I tried to use NI4461 card for this. But for DC output function calls , I am getting a glitch before the waveform gets stabilized to the DC output value. The same observation was repeated when the card was tested through Measurement and Automation. Is this due to any limitation in the card? Can this card be used for general DAC applications ?

 

 

Regards,

Anandu

[dsb@NI · Accepted solution]

Did the 'glitch' look like this?:

The 4461 is a dynamic signal acquisition device with all of the anti-imaging and anti-aliasing features that this designation entails. The acquired signal above is expected behavior because the onboard filters attenuate signal components with frequencies greater than 0.4*Fs. If you are seeing something different, post a screenshot and some code so the community can help more.

Generally, dynamic signal acquisition devices are designed to generate and acquire dynamic signals such as those found in sound and vibration applications. Use M-Series and X-Series devices to get the best performance value for DC applications.

[anandu]

Thank you.


This was the same problem that I was facing. I want to ask you one more question.

 I tried to output the DAC waveform at different output sampling rates. I used the sample program given by National Instruments for Analog Output using internal clock(VC++).   But for  low sampling frequencies (less than 100Hz), the whole waveform appears to be truncated in time domain. The truncation is so severe that it cannot be neglected.Why is it so?

Regards,

Anandu

[dsb@NI]

Verify that the device supports the sample rate you have requested and that you are not getting coercion or errors. Also, some people might describe the effects of filter delay as 'truncation'. You can find the ADC and DAC filter delays in the NI 446x Specifications available online.

Again, screenshots and/or code can eliminate some of the guesswork in trying to help.