Since commercial loggers face several issues when it comes to cave monitoring, we developed our own device (CORA; http://scholarcommons.usf.edu/ijs/vol41/iss2/13). After a few updates both in the SW and HW to ensure robust acquisition we now get some interesting time series spanning several years. The logger works with normal D-cells and allows for monitoring CO2, P, T over a full year at 4hrs intervals. Time intervals can of course be programmed manually. Let me know if you need some more info about it,