Figure 1-1 shows a typical design-to-deployment flow, starting with evaluation on an EVM and ending in the final application use case. At each stage in this flow, RH accuracy errors can be introduced. To effectively troubleshoot root cause for RH accuracy errors, TI recommends beginning by identifying the stage at which the error first appears, then tracing the issue backwards. For example, if RH accuracy errors are detected during evaluation with an evaluation module (EVM), then the errors must be related to environmental effects, heating effects, chemical exposure, or incorrect prototype/production testing methodology. This is because the EVM offers a known good PCB design and assembly process.

Figure 1-1 RH Sensor Design Example Timeline

The different sources of RH error are color coded in Figure 1-1, and are discussed further in the following sections of this document:

• Chemical contamination is discussed in Assembly, Soldering, and Manufacturing Processes, Storage and Handling, and Chemical Contamination.
• Incorrect measurement methods are discussed in Test Setup and Environment.
• Thermal effects and gradients are discussed in PCB and Enclosure Design Considerations, Storage and Handling, and Test Setup and Environment.
• RH drift over time is discussed in Storage and Handling and Operating Conditions: Application Environment Conditions and Effects
• Rehydration is discussed in Rehydration Post-Assembly
• Physical effects & damage are discussed in Assembly, Soldering, and Manufacturing Processes, Storage and Handling, and Chemical Contamination.
• Environmental effects are discussed in PCB and Enclosure Design Considerations, Assembly, Soldering, and Manufacturing Processes and Operating Conditions: Application Environment Conditions and Effects.