1) I do not know what the lowest hardware timed rate the USB-6341 can support is, but it almost certainly is much slower than 1 Hz. In addition to setting the timing through the DAQ Assistant or the DAQmx VIs, you can also reduce the data after it is acquired. For example you could accumulate the 1 Hz data for 1 minute, take the average of the 60 samples, save the average and discard the original data. The advantage of doing it the latter way is that you do not need to wait a long time to stop the program. Suppose you set the DAQ Assistant to sample one time per minute. If you press the stop button immediately after it takes a sample, it will be another minute before it actually stops.
2) A chart will display the data graphically over time. A chart has a built in buffer (called the Chart History). That can be read through a property node. However, your VI currently writes the data to a file on each iteration of the loop so it is not necessary to save the chart history - it is the same data.
You should probably run your Fit VIs one time before the loop starts. There is no need to recalculate the slopes and intercepts (which do not change unless your transducers change) on each iteration of the loop.
Lynn
