Data logging shield
Here's a handy dedicated and well-designed data logging Arduino shield.
You can get going within an hour - saving data to files on any FAT16 or FAT32 formatted SD card, to be read by any plotting, spreadsheet or analysis program.
The included Real Time Clock timestamps all your data with the current time, so that you know precisely what happened when!
SD card interface works with FAT16 or FAT32 formatted cards. 3.3v level shifter circuitry prevents damage to your SD card.Real time clock (RTC) keeps the
time going even when the Arduino is unplugged. The battery backup lasts for years.
Included libraries and example code for both SD and RTC mean you can get going quickly
Prototyping area provided for soldering connectors, circuitry or sensors.
Onboard 3.3v regulator is both a reliable reference voltage and also reliably runs SD cards that require a lot of power to run
ADAFRUIT TUTORIALS PDF
Links to SD LIBRARY , RTC LIBRARY