Interface electronic system for measuring air acidity with optical sensors

Environmental acidity is a key parameter in Cultural Heritage conservation issues since it has a direct impact on degradation of both exposed and stored materials. Unfortunately, most of the acidity sensors now available are electrodes, which are not able to measure pH in gaseous phases and, therefore, are not suitable for measuring the environmental acidity of the air. This paper describes the development of an interface electronic system designed for the practical application and using of environmental acidity sensors prepared by the Sol–Gel procedure. These chemical sensors were investigated previously. They have optical response: their color changes reversibly depending on the pH of the surrounding environment (air). A simple portable unit with a wireless ZigBee interface has been designed and developed to measure the environmental acidity in museums, showcases, store and exhibition rooms and several Cultural Heritage buildings. Main achievements of the interface electronic system have focused, on the one hand, on conversion of the optical signal of sensors into an electric current and, on the other hand, on the computer interfacing to obtain quantitative data of environmental pH. Quantitative data are obtained through the calibration curve of sensors and the software designed for managing the whole system.