I am using Labview with an SCXI1100 chassis. For analog input, I have an 1125 and am adding an 1104C. The DAQ card is a 6052E. The application is ATE for PWM power supplies. Most of the acquisition required is relatively low frequency, however - since the card and the 1104 sample at 333kHz, I should be able to pick up the 20-40kHz gate drive waveforms, and extract frequency, voltage, duty cycle, etc. But here's the question:
The cards themselves have 10kHz lowpass filters. What kind of filters? Chebyshev? Butterworth? Etc. Mathematically, I need to figure what exactly I am going to get out of the card. Is it just going to be attenuated? By how much? What's the noise floor at this frequency?
The manual on page A-3 has some useful information. I am posting it below. Additionally, I found that the SCXI-1104 series use a two-pole RC Butterworth filter. As you'll see in the notes below the 10kHz cutoff is the -3dB point for the filters.
Filters Cutoff frequency (?3 dB) SCXI-1104 ............... 2 Hz SCXI-1104C ............. 10 kHz NMR (60 Hz) ............ 40 dB (SCXI-1104) Step response (either gain) Accuracy SCXI-1104 SCXI-1104C To 0.1% 1 s 200 ms To 0.01% 10 s 1 ms