Ceramic capacitive rain sensor avoids false positives

Capacitive sensing is a technology based on the change in capacity determined by the change of the dielectric constant of the material separating the electrical conductors (plates) of the capacitor following the action of external agents.

Capacitive sensing is becoming a popular technology to replace optical detection methods and mechanical designs for applications like proximity/gesture detection, material analysis and rain/humidity detection, because it offers more reliable and accurate measurements than optical ones.

The sensor has IDT electrodes on one side of the alumina substrate, while a resistive heater and a temperature sensor are placed on the opposite side. The rain sensitive area, which in dry conditions assumes the nominal value of 100pF. Moreover in presence of the rain, the capacitance goes to high values compared to dry conditions and the ratio changing is over 300%.

The integral and configurable heater is provided to ensure that the detection surface dries quickly, protecting the surface from fog, condensed moisture and frost. It also can be disabled when power consumption is critical.

The alumina substrate and the glass sensitive layer makes the sensor immune to water and moisture absorption, ensuring high resistance and long duration.

Moreover, thanks to the thermal conductivity of the ceramic, the heat emitted by the heater on the back of the sensor is immediately transferred to the upper surface, making the sensor more sensitive than other technologies.

Furthermore, while resistive rain sensors are sensible to corrosion and contamination, the Telecontrolli capacitive rain sensor doesn't suffer from these disadvantages, making it suitable for any type of application - including irrigation systems for agriculture, automotive wiper systems, weather stations, and applications for home and building automation.