sample and integrate analog signal

[WernerGobel]

Hello,

is there an easy way to sample an analog input signal at high rates (3 - 4 MHz), for example using the 6115 board, and integrating (summing up) the obtained values at lower time steps. These time steps (at maximum 400kHz) are given by ttl pulses on a PFI or RTSI line. All sampled and acquired values between two following pulses on the PFI/RTSI line shall be summed up.

What's the best way to implement this?

Thanks a lot for any help or suggestions!!!

[Jochen]

As there is no way to do the calculations onboard and in respect of the high acquisition rates the task is definitely not trivial. Here is an idea how to do that:

1. Configure a counter of the 6115 for buffered event counting
2. Configure the counter to count the sample clock of your analog acquisition (the counter will count with a rate of 3-4 MHz).
3. Route the time step signal (your 400 kHz signal) to the Gate of the counter.
4. Start the counter
5. Start the analog acquistion

With this configuration you should get two arrays: One array contains the analog data, the other one contains the counter data. The counter data represents the indices in your analog data array where the time step signal transitioned from low to high. With these data you can decide which parts of the analog data array need to be summed.
Of course this works only as an offline analysis after the acquisiton is finished. If you really need to do the summation with a rate of 400 kHz while the acquisition is running I think this will not be possible with standard hardware. I think this is even too fast for the fastest DSPs available but maybe someone else can comment on that.

Best regards

Jochen Klier
National Instruments Germany