Campbell Scientific SDM-IO16 16-Channel Input/Output Module

If you are short on digital I/O channels the SDM-IO16 is the solution. 

It adds 16 additional channels to the CR800/CR850, CR1000, CR3000 and CR6 dataloggers. Up to 15 SDM-IO16 modules can be connected, for a total of up to 240 digital I/O channels in addition to the datalogger's on-board I/O.