This application note defines a basic iButton datalogger and shows how these products can vary to track temperature and/or humidity data. Typical applications are presented. The note explains how the datalogger is constructed, tested, and certified to pass various safety and EMI standards. Flexible and programmable, each iButton datalogger is designed to be setup (a step called ‘missioning’) by the user to collect data for an application. The software for missioning is discussed and made available to the reader. The formats for data presentation are shown.