1. Overview & Purpose

️· Sensor Type: Capacitive humidity and temperature sensor (monolithic – both are on the same chip).
️· Intended Use: Accurate measurement of humidity and temperature for various applications.
️· Manufacturer: SENSIRION

2. Specifications & Performance

️· Humidity Measurement:
- Ranges: Normal operating conditions specify -40 to 85°C and 0-100% RH. Extended conditions are listed as well (see figure 11).
- Accuracy: Not explicitly stated, but mentioned as reversible shifts (+2% RH) after specific tests.
- Dewpoint Measurement: Excellent for dewpoint calculation (see application note).
️· Temperature Measurement:
- Linearity: Very linear due to bandgap PTAT design.
- Conversion Formula (Digital to Temperature): Provided (see Table 5). VDD dependent.
️· Calibration: Calibration data is supplied with the sensor.
️· Qualification Tests: The document lists a series of qualification tests performed to ensure reliability (see Table 5).

3. Environmental Considerations & Operating Conditions

️· Operating & Storage Temperature: -40°C to 85°C (normal operation).
️· Exposure to Chemicals: Vapors can affect the polymer layers. Reconditioning is recommended.
️· Reconditioning Procedure: Baking at high temperature followed by re-hydration (detailed in section 13).
️· Materials: Careful selection of materials near the sensor is crucial (see section 13). Avoid humidity-absorbing materials.
️· Light: Not light-sensitive, but prolonged UV exposure can affect housing.
️· ESD Immunity: Qualified according to MIL STD 883E.
️· Wiring: Signal integrity needs consideration (parallel wires can cause interference).

4. Key Formulas & Tables

️· Temperature Conversion:
- VDD (Voltage Supply) dependent. See Table 8 for specific formulas.
️· Tables Provided: (Key values listed above are pulled from these.)
- Table 5: Temperature Conversion Coefficients
- Table 5: Qualification tests
- Figure 11: Operating conditions

5. Application Information

️· Dewpoint Measurement: SHTxx allows for very good dewpoint measurements, refer to application note.
️· Wiring Parallel wiring should be avoided as it can cause signal integrity issues.

Key Takeaways

️· Accuracy Dependent on Environment: The sensors are generally accurate but can be influenced by extreme conditions and chemical exposure. Reconditioning is vital for maintaining accuracy.
️· Material Selection is Important: The materials used around the sensor significantly affect response time and accuracy.
️· Signal Integrity: Pay attention to wiring practices to avoid interference.
️· Calibration is Key: Always refer to the supplied calibration data.