An Optical Relative Humidity Sensing System

The relative humidity (RH) of air is an important parameter that needs to be measured in many industries. Brook et al.^1,2] studied the response of Nafion films containing Crystal Violet to the relative humidity; Raimundo et al.^3] investigated the composition of Nafion-Crystal Violet films and their casting processes. In this paper, the sensing film was prepared by entrapped Crystal Violet in the commercial Nafion film. The dry air was commercially available and the 100% RH air was obtained by bubbling dry air into a series of bubbling flasks filled with deionized water. A spectrophotometer was employed to monitor the absorption changes of the film at the range of 400nm to 700 nm.