Next, the HDC3020 was tested overtemperature to make sure that the HDC3020 can reliably detect a small volume of water ingress. After studying the three-drop test data at varying conditions, the slew rate threshold of 10m%RH/s was chosen to detect a water ingress event for the given test enclosure.

The results for the three drop tests across all temperature and humidity conditions are summarized in Table 5-1 and Figure 5-8. In all cases, the ingress event was detected within 40 seconds, and in most cases within a few seconds. As shown, drier conditions produced a much higher peak RH slew rate (up to 106.0m%RH/s in cold, dry air) compared to more humid starting conditions. Drier conditions also allowed the ingress event to be detected more quickly, as fast as 1.5sec in hot, dry air (using a 2Hz automatic measurement rate). The peak slew rates at cold temperatures were higher than at hot temperatures; for example, compare the cold or humid and hot or humid test results. This behavior can be explained because the equilibrium saturation vapor pressure is lower at cold, so the environment’s capacity for water moisture is lower, thus small changes in water content result in larger changes in RH. Even in the worst-case tested scenario at hot and humid conditions, the humidity spike caused by the ingress event (22.6m%RH/s) comfortably exceeded the 10m%RH/s threshold. This confirms that the chosen threshold is appropriate across a range of realistic environmental conditions.