If you are facing the need of reading and storing sensor data (analog and digital signals) and do not want to spend a lot of money on an off-the-shelf data logger, I may have the solution for you.
Based on my own need for a simple and cheap system that can store analog data from various sensors (mainly 0-5v ones), I have developed an Arduino-micro-based datalogger that stores data to an on-board microSD card.
This is how it works:
1- Insert a microSD card on the slot (if you don't, the red LED will lit and nothing else can be done),
2- Connect analog or digital sensors (up to 5V max) to the 4 analog inputs and 1 digital (interrupt) input,
3- Supply 5V to the system, either from the USB @ Arduino Micro or the specific blue connector on the board,
4- Press the green button; the data will be logged into the microSD card on '.csv' format, from time to time (adjustable on the Arduino code),
5- The system will log data for as long as there is power supplied.
Here is an overview of the system; why I made it and how it works:
The full explanation, code and schematics is hosted on my personal blog: