Peek at an analog input buffer?

[jas3600]

I have an application where I am using a very slow PID loop to control the quiescent level that is read at an analog input. An external event creates a spike on this input that is very fast compared to the PID loop response.  I would like to recored this spike event and store it for analysis.

Using a pretriggered task seems to be the best solution for capturing the spike event but I am  not sure of how to aquire the data needed for the PID loop.

Running two analog input tasks on the same PXI card, one slow speed for the PID loop and one high speed for the spike, didn't seem to work.

Is there a way to peek at the pretrigger task's buffer to periodocally grab data for the PID input?

[Ryan_V[DE]]

jas3600,

Here is an example VI which changes the "Read Relative Property" to correspond to be the most recent sample and "peeks" at this value in the buffer. It then returns the property to read relative to the first pretrigger sample (the default for a referenced triggerd acq.) and checks to see if all samples have been acquired. Please let me know if you have any questions on it.

Hope this helps,