A PCB Sensor for Detecting Icing Events

Ice formation can be problematic on surfaces, such as roads, bridges, wings, and sensitive plants. A simple low-cost sensor for detecting the formation of ice has been developed using standard low-cost commercial printed circuit board fabrication techniques. The sensor consists of a capacitive interdigitated electrode structure, realized in the top Cu layer of the circuit board and covered with a polymeric solder mask. The sensor's capacitance is measured at 1 and 64 kHz, and then, the ratio of the two capacitances is computed. The ratio is then compared with a threshold value of 2.0. Icing results in the capacitance ratio exceeding 2.0, whereas dry conditions or water result in a ratio of less than 2.0. This technique exploits the dielectric relaxation properties of ice, in which ice has a high dielectric constant below the relatively low dielectric relaxation frequency of ≤3 kHz and a low dielectric constant well above that frequency. The sensor was evaluated in air, water, and ice over a temperature range of -30 to 34 °C and successfully identified ice every time.