Sampling rate and number of samples I am doing an experiment where i have to excite a plate and scan a region on it using a laser signal. 
I am acquiring the signal from the laser continuously using an NI daq tool. i then have to divide this  signal into a set of discrete intervals, (each corresponding to a 1 mm segment in the scanning region), in which the time between the segments should have integer number of harmonic excitation wave cycles.
The speed that the laser moves in on the scanning region is 1 mm/min. 
The excitation frequency is 100Khz, and the sampling rate of the daq tool is 1Msps.
however, i am not sure what should be the number of samples N for the tool?
Sampling Rate of the daq tool tells you how many measurement samples will be collected per second. So, if the sampling rate $f_s=1Msps$, it means that your daq tool is collecting $10^6$ samples per second.