6 Summary

Using a humidity sensor, such as HDC3020, presents a new method for water ingress and leak detection based on an RH slew rate detection algorithm. A sharp rise in relative humidity (measured as an RH 10-second slew rate) signals a water leak. This method allows a single sensor to cover the whole enclosure by sensing water vapor, catching leaks regardless of where the leaks occur. These findings can be applied to both semi-open and closed systems.

Extensive testing across temperatures 10–50°C and humidity 10–70%RH demonstrated that even a small leak (0.07mL of water in a 1.7L enclosure) triggers a clear humidity spike. A threshold of 10m%RH/s reliably detected such leaks in less than 40 seconds using the tested 1.7L enclosure, while avoiding false alarms from ambient humidity changes. The method was also robust across all tested conditions, including hot/cold and humid/dry extremes. This approach provides early warning of leaks and water ingress with minimal hardware, employing only a small humidity sensor and simple firmware logic. This outperforms traditional methods by detecting water ingress anywhere in the enclosure and by differentiating true leaks from background humidity drift.

The HDC3x product family (including automotive-grade variants such as HDC3020-Q1) is TI’s latest generation of humidity sensors and is suggested to implement this leak detection method. The HDC3020 digital RH sensor and HDC3120 analog-output RH sensor are both available in a standard open cavity WSON package. Also available are package variants HDC3021 and HDC3022, which offer the same electrical and RH performance as HDC3020. Notably, the HDC3022 includes an IP67 rated PTFE filter to protect the center cavity from dust and water. This water detection algorithm is not only easy to implement, but this can be adjusted for different enclosure volumes and anticipated amounts of water entering a system. Making sure the enclosure is either sealed or properly vented prevents large ambient humidity swings, so that any leak-induced humidity rise is much more pronounced than normal environmental changes. The test results indicated that the detection algorithm can use a slew rate threshold of 10m%RH/s, however the designed for threshold needs to be adjusted based on empirical evaluations of a specific enclosure size’s air volume and the required sensitivity (for example, amount of water ingress that must be detected).

Figure 6-1 HDC3x Product Family Package Options