ABSTRACT
This chapter reviews the most widely adopted techniques for humidity sensing. It focuses on material choice, design parameters, and sensor characteristics. Humidity is the water vapor content present in the air or other gases. The trace amount of water present can drastically change the physical, chemical, electrical, and mechanical properties of the material. Therefore, it is equally important to detect or monitor the humidity for diverse applications. A double electrochemical cell containing a solid electrolyte with oxygen ion conductance and another cell consisting of a solid electrolyte with hydrogen ion conductance was developed for humidity sensing. The inorganic halide perovskites have also been explored for humidity sensing owing to their interesting features like good chemical and thermal stability. Several capacitive-based sensors have been extensively tested for humidity sensing applications as these kinds of devices convert humidity change into their respective capacitance.
