SNAA420A June   2025  – August 2025 HDC3020 , HDC3020-Q1 , HDC3021 , HDC3021-Q1 , HDC3022 , HDC3022-Q1 , HDC3120 , HDC3120-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Motivation
    2. 1.2 The Physics of Humidity and Water Ingress
  5. 2Test Methodology
  6. 3Assumptions
  7. 4Proposed Algorithm Using Slew Rate Threshold
  8. 5Test Results
    1. 5.1 Test Results at Indoor Ambient Conditions
    2. 5.2 Test Results at Hot and Cold Temperature Conditions
    3. 5.3 Vent Submersion and Air Exchange Tests
  9. 6Summary
  10. 7References
  11. 8Revision History

Abstract

Water ingress or intrusions can be a significant threat to critical electronic components used in many applications, including automotive and enterprise systems such as electric power steering (EPS), EV battery packs, LiDAR and liquid-cooled servers. This application note presents a humidity sensor-based detection method utilizing the HDC3020 sensor to rapidly identify water ingress in sealed or vented electronic enclosures, using the slew rate (for example, rate of change) of relative humidity (RH) as an indicator for water ingress events. Specifically, the RH slew rate can be calculated over a 10-second window and compared against a threshold to detect when a water ingress event occurs. This approach reliably detects even minor leak events (≤0.07mL in a 1.7L enclosure) within seconds. This outperforms conventional PCB-trace electrode water sensors, enhancing system reliability, reducing false positives, and simplifying sensor deployment.

Water Ingress Detection Using RH Slew Rate ThresholdFigure 1-1 Water Ingress Detection Using RH Slew Rate Threshold