Methods and types of devices used for measuring humidity use different measurement principles, materials and varying configurations, making it difficult to compare capabilities. Data presented provides detailed information on types of humidity sensors accompanied by an analysis of their strengths and weaknesses, allowing for comparison and selection of the best method for specific applications. The first volume focuses on devices based on optical principles of measurement, the second volume focuses on electronic and electrical devices. Numerous strategies for the fabrication and characterization of humidity-sensitive materials and sensing structures are described throughout. The second volume is entirely devoted to the consideration of different types of solid-state devices developed for humidity measurement. The third volume offers an analysis on various humidity sensitive materials and sensor technologies used in the fabrication of humidity sensors and methods acceptable for their testing.