Sensor Specifications — Technical Reference
For sensor recommendations and buying guidance, see Recommended Sensors.
This page provides technical reference for firmware developers and hardware integrators.
Quick Reference
| Sensor | Type | Measurements | Interface | I2C Address | Calibration Period |
|---|---|---|---|---|---|
| SHT45 | T/H | Temperature, Humidity | I2C | 0x44 | Immediate |
| SHT41 | T/H | Temperature, Humidity | I2C | 0x44 | Immediate |
| TMP117 | Temp | Temperature | I2C | 0x48 | Immediate |
| SCD30 | CO2 | CO2, Temperature, Humidity | I2C | 0x61 | 7 days (if ASC enabled) |
| SCD4x | CO2 | CO2, Temperature, Humidity | I2C | 0x62 | 7 days (if ASC enabled) |
| SPS30 | PM | PM1.0, PM2.5, PM4, PM10 | I2C/UART | 0x69 | Immediate |
| MS5611 | Pressure | Pressure, Temperature | I2C/SPI | 0x76/0x77 | Immediate |
| BMP390L | Pressure | Pressure, Temperature | I2C | 0x76/0x77 | Immediate (one-time offset) |
| TSL2591 | Light | Lux (visible + IR) | I2C | 0x29 | Immediate |
| LTR-390UV | UV | UV Index, Ambient Light | I2C | 0x53 | Immediate |
| INA226 | Power | Voltage, Current, Power | I2C | 0x40-0x4F | Immediate |
| INA219 | Power | Voltage, Current, Power | I2C | 0x40-0x4F | Immediate |
| INMP441 | Noise | Audio (I2S) | I2S | N/A | Immediate |
| SGP41 | Air Quality | VOC Index, NOx Index | I2C | 0x59 | 12 hours |
| BME680 | Environmental | Temp, Humidity, Pressure, Gas | I2C | 0x76/0x77 | 48 hours |
| PMS5003 | Particulate | PM1.0, PM2.5, PM10 | UART | N/A | 1 hour (fan warmup) |
| CM1106-C | CO2 | CO2 | I2C | 0x31 | 15 days (if ABC enabled) |
| AHT20 | T/H | Temperature, Humidity | I2C | 0x38 | Immediate |
| BMP280 | Pressure | Pressure, Temperature | I2C | 0x76/0x77 | Immediate |
Sensor Priority Hierarchies
The firmware uses a priority system when multiple sensors measure the same parameter. Lower priority numbers are preferred.
Temperature
| Priority | Sensor | Stability | Notes |
|---|---|---|---|
| 1 | SHT45 | 5-star | Best T/H combo, zero maintenance |
| 2 | SHT41 | 5-star | Budget T/H, same stability |
| 3 | TMP117 | 5-star | Best temp-only if +-0.1C needed |
| 4 | SCD30 | 5-star | Good accuracy from CO2 sensor |
| 5 | SEN55 | 4-star | Multi-sensor module |
| 6 | BME280 | 3-star | Backup from integrated sensor |
| 7 | BME680 | 2-star | Not recommended |
| 8 | AHT20 | 2-star | Not recommended — drifts |
Humidity
| Priority | Sensor | Stability | Notes |
|---|---|---|---|
| 1 | SHT45 | 5-star | Best humidity sensor |
| 2 | SHT41 | 5-star | Budget option, same stability |
| 3 | SCD30 | 5-star | Good accuracy from CO2 sensor |
| 4 | SEN55 | 4-star | Multi-sensor module |
| 5 | BME280 | 3-star | Backup from integrated sensor |
| 6 | BME680 | 2-star | Not recommended |
| 7 | AHT20 | 2-star | Not recommended — drifts |
CO2
| Priority | Sensor | Stability | Notes |
|---|---|---|---|
| 1 | SCD30 | 5-star | Dual-channel NDIR = best long-term stability |
| 2 | SCD4x | 4-star | PAS technology, smaller form factor |
| 3 | SEN66/68 | 4-star | Multi-sensor module with CO2 |
| 4 | CM1106-C | 1-star | Not recommended — ABC unreliable indoors |
Pressure
| Priority | Sensor | Stability | Notes |
|---|---|---|---|
| 1 | MS5611 | 4-star | Zero calibration, excellent stability |
| 2 | BMP390 | 4-star | Best accuracy, needs one-time offset |
| 3 | BME280 | 3-star | Integrated T/H/P |
| 4 | BMP280 | 3-star | Budget, solder drift risk |
| 5 | BME680 | 2-star | Not recommended for pressure |
Particulate Matter
| Priority | Sensor | Stability | Notes |
|---|---|---|---|
| 1 | SPS30 | 5-star | 10+ year lifetime, contamination resistant |
| 2 | SEN55 | 4-star | Multi-sensor module |
| 3 | PMS5003 | 2-star | Not recommended — drifts, needs cleaning |
| 4 | SDS011 | 2-star | Not recommended — drifts, needs cleaning |
VOC/Air Quality
| Priority | Sensor | Stability | Notes |
|---|---|---|---|
| 1 | SGP41 | 2-star | Not recommended — relative only, but best available |
| 2 | SEN55 | 4-star | Multi-sensor module, same VOC limitations |
| 3 | SGP40 | 2-star | Not recommended — relative only |
| 4 | BME680 | 2-star | Not recommended — BSEC complexity |
Light
| Priority | Sensor | Stability | Notes |
|---|---|---|---|
| 1 | TSL2591 | 4-star | High dynamic range, dual channel |
| 2 | VEML7700 | 2-star | Erratic above 70 klx |
| 3 | BH1750 | 3-star | Budget option |
UV
| Priority | Sensor | Stability | Notes |
|---|---|---|---|
| 1 | LTR-390UV | 4-star | Less prone to solarization |
| 2 | VEML6075 | 2-star | Degrades in direct sunlight |
Power Monitoring
| Priority | Sensor | Stability | Notes |
|---|---|---|---|
| 1 | INA226 | 5-star | 16-bit precision |
| 2 | INA219 | 5-star | 12-bit, budget option |
Calibration Periods Summary
During calibration, sensor data may be suppressed to prevent inaccurate readings from affecting your database.
| Sensor | Calibration Period | Trigger | Notes |
|---|---|---|---|
| SHT4x | Immediate | N/A | Factory calibrated for life |
| TMP117 | Immediate | N/A | NIST traceable, factory calibrated |
| SCD30 | 7 days | ASC enabled | Needs 1h exposure to ~400ppm fresh air daily |
| SCD4x | 7 days | ASC enabled | Needs 1h exposure to ~400ppm fresh air daily |
| SPS30 | Immediate | N/A | Factory calibrated, contamination resistant |
| MS5611 | Immediate | N/A | Factory calibrated |
| TSL2591 | Immediate | N/A | Factory calibrated |
| LTR-390UV | Immediate | N/A | Factory calibrated |
| INA226 | Immediate | N/A | Factory calibrated |
| CM1106-C | 15 days | ABC enabled | ABC configurable 1-30 days (Winsen default 7-15) |
| SGP41 | 12 hours | Always | 10s warmup + algorithm conditioning |
| BME680 | 48 hours | Always | BSEC gas sensor burn-in period |
| PMS5003 | 1 hour | Always | Fan/laser warmup |
Full Spreadsheet
Download the complete sensor comparison spreadsheet with all 50+ sensors, including maintenance scores, stability ratings, accuracy details, prices, technologies, interfaces, and Arduino library references.
Datasheets
All datasheets are available on the Recommended Sensors page.