
Jakub Felcenloben over at Electronics Lab has written up documentation on his latest project called miniLOG, a basic data logger:
miniLOG is a precise standalone voltage logger that save the data on a SD card. It has 4 basic analog channels:
- one has 12bit resolution for voltage measurements,
- two channels have 10bit resolution for voltage measurements and
- one channel has 10 bit resolution for current measurements.
Input voltage range is 0-25V and current range is 0-500mA. The data are written on a simple .txt file on SD card and can be further proccessed using spreadsheet software.

Awesome project! I did something similar to a solar powered weather station a while back i built using the GR Sakura Board!
It has an on board microSD card. It would be a lot better if you store the data in a csv format rather than plane text! Excel picks up the data directly making it easy to analyse.
As always the project i did is OpenSource here.
Video
Cheers,
Rohit