I plan to purchase one of these modules NI 9230 or NI 9234. Both seem to have similar configurations except the number of inputs (3 and 4 respectively) and sampling frequencies (12.8 kS/s/ch and 51.2 kS/s/ch respectively) and few other minor differences. I need to acquire data from two accelerometers (at around 0.1-2khz) and an impact hammer. Which of these modules would be suitable since the price difference is about INR 1 lakh.
I need to acquire data from two accelerometers (at around 0.1-2khz) and an impact hammer.
Per Nyquist, if you want to see a 2kHz signal, you have to sample at least 4kHz. To actually get a good look of the full bandwidth, you really need to be more around 10x the bandwidth. This would put you around 20kHz sample rate. Since you have 3 channels, the 9230 will put you at 12.8/3 = 4.27kHz. The 9234 would give you a max sample rate of 51.2/3 = 17.07kHz. So I would go with the 9234 and max out that sample rate just so you can get a decent resolution at the 2kHz frequency.
By my experience on low shock, you will be happy for every sample.
I even quenstion the 2kHz upper bandwidth until proved by measurements with higher bandwidth 😉
Even at shock durations of 5ms ore longer, you can have significant energy at frequncies beyond 2 kHz.
So I'm with crossrulz... get the one with higher bandwidth.