Possibilities and limitations for onboard data acquisition
First of all your idea project is feasible. And to answer to your questions:


There is no right Arduino for your project simply because theoretically every Arduino board can do the job. But as you said it has to be portable you might use Arduino nano/mini or even Uno if you have enough room or space.
The acquisition rate depends on the on the type of sensor you have. So if you have let's say one analog reading you can use the built in function in Arduino which is capable of making about 10000 readings at time. So if you have multiple outs you can easily for the calculation. There are also sensors which has a digital output in this case in order to read your value you communicate with Tue sensor board through Two wire interface or I2C communication interface, for this there is a library you can use. Usually the speed at which this communication work s very high, at 100kHz( if I'm not wrong).

3.Yes you can save data on the SD card until you don't exceed the memory or the battery doesn't die.


I have a suggestion for your project, as you're going to acquire some sort of data and then analyze it on your computer, do less calculations on your Arduino board and let the PC handle the hard work.

Useful links:


Reference to the two wire communication: http://arduino.cc/en/reference/wire
Reference to the SD card reading on Arduino: http://arduino.cc/en/Reference/SD