Environmental Sensors#

Temperature, humidity, barometric pressure, and air quality are the most frequently measured quantities in embedded systems — from HVAC controllers and weather stations to cold-chain monitors and indoor air quality devices. The sensors themselves range from simple analog thermistors to complex multi-parameter digital ICs that report temperature, humidity, and pressure over I²C in a single transaction. Despite the variety, the integration patterns repeat: configure the sensor’s measurement mode and resolution, trigger or wait for a conversion, read the raw data over a serial bus, and apply the manufacturer’s compensation formula to get physical units.

This subsection covers the major environmental sensor families, their bus-level integration, and the firmware patterns that apply across dozens of similar devices.

Pages#

• Temperature Sensing (NTC, RTD, Digital) — Thermistor front-end circuits, RTD bridge configurations, and digital sensors (DS18B20, TMP117) with their bus protocols and accuracy tradeoffs.
• Humidity & Barometric Pressure — Capacitive humidity sensors, MEMS barometric pressure devices (BME280, BMP390), compensation algorithms, and altitude estimation from pressure.
• Gas & Air Quality Sensors — Metal-oxide (MQ-series), electrochemical, and MEMS gas sensors (SGP40, BME688), baseline calibration, and interpreting air quality indices.
• Environmental Sensor Bus Patterns — Shared I²C bus topologies, address conflicts, multi-sensor polling strategies, and power management for battery-operated environmental loggers.