EasyLog High Accuracy Temperature and Humidity USB Data Logger - 

This standalone data logger measures and stores up to 16,382 relative humidity and 16,382 temperature readings over 0 to 100%RH and -35 to +80°C (-31 to +176°F) measurement ranges. The user can easily set up the logger and view downloaded data by plugging the data logger into a PC's USB port and running the purpose designed downloadable software under Windows 2000, XP, Vista, 7 & 8 (available as a free download from www.easylogusb.com). Relative humidity, temperature and dew point (the temperature at which water vapour present in the air begins to condense) data can then be graphed, printed and exported to other applications. The data logger is supplied complete with a long-life lithium battery, which can typically allow logging for up to 3 years.