Piezoelectric quartz crystal humidity sensor using chemically modified nitrated polystyrene as water sorbing coating

A new coated piezoelectric crystal (CPC) humidity sensor has been developed based on surface chemically modified coatings of nitrated polystyrene (NPS). Its frequency response to relative humidity (RH) has been examined. The CPC detector has a time response of less than 3 s, exhibits high sensitivity (up to 40 Hz per %RH) and very good performance reproducibility and stability upon long-term calibration for more than 3 months. No interference with the frequency response to water vapours in the presence of corroding gases such as SO2 and NO2 has been observed. The factors contributing to optimization of selected performance characteristics have been discussed.