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 BME688 
 Temperature sensors 

Advanced environmental sensor with gas detection and AI capabilities for air quality and smart sensing applications.

 Interface

I²C 

 Measurement range
-40 / 125°C

 Humidity range
0% → 100%

 Pressure gauge (hPa)
300 → 1100

Temperature accuracy

+/-0,5K

Humidity accuracy
+/- 3 %

 Pressure precision
+/- 1 hPa

 Internal resolution
16 to 20 bits

 power supply voltage
1,71 → 3,6 V

 Sampling rate
1 to 100 Hz

 Typical current
3,6µA(active)

 Price
Medium

What is a BME688 sensor ?Operating principleExample of data outputPrinciple diagram (I2C connection)Application areas

What is a BME688 sensor ?

The BME688 is Bosch's most advanced environmental sensor.

It combines:

  • the three classic sensors of the BME280 (temperature, humidity, pressure),
  • a gas sensor (MOX) capable of identifying volatile organic compounds (VOCs),
  • and embedded intelligence via the BSEC2 library (Bosch Software Environmental Cluster).

The great interest of the BME688 lies in its ability to be AI-trained to recognize specific odor profiles (smoke, fermentation, stale air, burnt plastic, etc.).

Operating principle

The BME688 operates in four steps:

  1. MEMS sensors measure temperature, humidity, and pressure.
  2. A MOX (Metal Oxide) gas sensor changes resistance according to ambient gases.
  3. A programmable internal heater adjusts the temperature of the gas sensor (200 to 400 °C).
  4. The BSEC2 algorithm transforms raw data into:
    • IAQ (Indoor Air Quality)
    • CO2 equivalent
    • VOC equivalent
    • Odor classification (AI mode)

I AQ = f(T, RH, P, R_gaz)

💡 The heating profiles and odor recognition are configurable via the Bosch AI Studio software.

Example of data output

Parameter Unit
 Typical example
Temperature °C 23,6
Humidity % RH 45,8
Pression hPa 1012,7
Gas resistance kΩ 68,3
IAQ (Indoor Air Quality) 0–500 54 (healthy air)
CO₂ equivalent ppm 472
VOC equivalent ppm 0,22

Principle diagram (I²C connection)

+3.3V
 │
[BME688]
 │ SDA ─────────┐
 │ SCL ─────────┤── [I²C Microcontroller]
 │ GND          │
 │ CSB / SDO ───┘ (config SPI / address)

💡 I²C Address: 0x76 (SDO=GND) or 0x77 (SDO=VCC).

Application areas

🌬️ Indoor Air Quality (IAQ) Monitoring

🧠 Odor Analysis / Specific Gas Detection (AI)

🏠 Home Automation, HVAC, Air Purification

🚗 Automotive Environmental Sensors

📱 Connected Devices, Smartwatches, Environmental IoT


Should I choose a BME688 sensor ?

Strengths points

  • 🧠 Smart environmental sensor (integrated AI)
         → Capable of identifying and classifying air profiles using Bosch AI Studio.
  • 🌍 4 sensors in 1→ Temperature, humidity, pressure, and gas — one single component, zero manual calibration.
  • 🎯 Bosch Precision and Stability
         → Each unit is factory calibrated and thermally compensated.
  • 🔋 Adaptive power modes
         → Allows for precise management of consumption based on the measurement frequency.
BME688 sensors

Weaknesses points

  • 🤖 Requires AI training
         → For specific detection (odors), the model needs to be trained using Bosch AI Studio.
  • 🔥 Gas sensor heating
         → Can consume up to 12 mA depending on the heating profile.
  • 📦 Higher cost
         → But justified by its advanced features and embedded AI.

Useful information

Here is some useful information regarding the BME688 sensors.

Address (hex)
 Name
 Description
0xE0 reset Sensor reset
0x74 ctrl_meas Temperature and pressure configuration
0x72 ctrl_hum Humidity configuration
0x71 config Duration of monitoring and filtering
0x50 → 0x59 data registers Raw data T, RH, P, gas
0x89 → 0xA1 coefficients Factory calibration data 
i2c_start();
i2c_write(0x76 << 1);
i2c_write(0x50);
i2c_start();
i2c_write((0x76 << 1) | 1);
read 10 bytes -> raw_t[3], raw_p[3], raw_h[2], raw_g[2];
i2c_stop();

temp = compensate_T(raw_t);
press = compensate_P(raw_p);
hum = compensate_H(raw_h);
gas = compensate_G(raw_g);
IAQ = f(temp, hum, gas);

💡 The compensation and IAQ functions are provided by the BSEC2 library.

3.3V ───────────┐
                │
               [BME688]
                │ SDA ───────┐
                │ SCL ───────┤── MCU (ESP32, STM32, Raspberry Pi…)
                │ CSB/SDO ───┘ (I²C or SPI)
                │ GND

💡 Pull-up resistors of 4.7 kΩ on SDA and SCL required if not integrated.

Step
 Action
1️⃣ Collect air data via BME688 + BME AI-Studio App
2️⃣ Label the scent profiles (coffee, clean air, plastic…)
3️⃣ Train the AI model on PC
4️⃣ Export the .bmeconfig file and load it into the microcontroller
5️⃣ The BME688 identifies the type of air encountered in real-time ✅
💡 The sensor thus becomes capable of "recognizing odors" in the field without an internet connection.
Parameter Range Max error
Temperature 0 → +65 °C ±0,5 K
Humidity 20 → 80 % RH ±3 % RH
Pression 300 → 1100 hPa ±1 hPa
IAQ 0–500 ±10% typical

💡 The IAQ (Indoor Air Quality) of the BME688 is compliant with WHO standards and can be converted to CO₂/VOC equivalents.

 We integrate any sensor into any probe 

Smooth tube probe

 Smooth tube 

Waterproof probe

 Waterproof

Bayonet probe

 Bayonet

Slot probe

 Slot

Ambient probe

 Atmosphere

Connection head probe

Termal block

Stick-in probe

Stick-in

Thread probe

Thread

Contact probe

Contact

Jacketed probe

Jacketed

PCBA Design

PCBA design

Winding probe

Winding

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