Sensor Selection Guide for IoT: Temperature, Humidity, Motion, Gas, Environmental

Sensor selection for IoT and embedded devices

Sensor Selection Guide for IoT: Temperature, Humidity, Motion, Gas, and Environmental Sensors

Every IoT device starts with a sensor. It's the component that actually touches the physical world, and choosing it wrong shows up in cost, accuracy, power consumption, and — worst of all — field reliability months after launch. Here's the practical guide we wish we'd had before our first production order, with part numbers and sourcing tips.

Temperature Sensors

Type	Accuracy	Range	Interface	Cost
NTC thermistor	±0.1°C	-50 to 250°C	Analog voltage divider	$0.10-0.50
RTD (Pt100)	±0.03°C	-200 to 850°C	Analog (needs excitation)	$3-50
Digital (I2C)	±0.2-1.0°C	-40 to 125°C	I2C/SPI	$0.50-3
Thermocouple	±1-5°C	-200 to 1750°C	Analog (mV, cold-junction comp)	$1-20

Popular digital sensors:

Sensirion SHT4x (temp + humidity, ±0.2°C, I2C)
TI TMP117 (±0.1°C, I2C, medical-grade accuracy)
Maxim DS18B20 (1-Wire, waterproof probe available)

Humidity Sensors

Sensirion SHT45 (±1.0% RH, I2C, industry standard)
Bosch BME280 (temp + humidity + pressure, single package)
Aosong AHT20 (budget Chinese alternative, ±2% RH)

Note: Humidity sensors drift over time, especially in condensing environments. Budget for recalibration or plan for sensor replacement every 2-3 years in harsh environments.

Motion and Position

Type	Technology	Range	Key Application
Accelerometer	MEMS capacitive	±2g to ±200g	Vibration monitoring, tilt
Gyroscope	MEMS vibratory	±125 to ±2000 dps	Drone stabilization
IMU (6-axis)	MEMS accel + gyro	Combined	Navigation, robotics
Hall effect	Magnetic field	0 to 30mT	Proximity, current sensing
Magnetometer	AMR/TMR	±10 gauss	Compass, metal detection

Popular IMUs:

TDK ICM-42688-P (ultra-low noise for drones)
Bosch BMI270 (ultra-low power for wearables)
ST LSM6DSO32 (accelerometer up to 32g)

Gas and Environmental

Sensor	Detection	Cost	Life	Application
CO2 (NDIR)	400-5000 ppm	$15-50	10+ years	Air quality, HVAC
PM2.5 (laser)	0-1000 µg/m³	$5-20	5-7 years	Air purifiers
VOC (MOX)	0-60,000 ppb	$3-10	5-10 years	Indoor air quality
Formaldehyde	0-1 ppm	$10-30	2-5 years	New home monitoring

Popular environmental sensors:

Sensirion SGP41 (VOC + NOx, MOX sensor)
Sensirion SCD41 (CO2, NDIR, ±40 ppm)
Plantower PMS5003 (PM2.5 laser particle counter)

Chinese Sensor Manufacturers

Goertek (歌尔) — MEMS microphones, largest MEMS sensor maker in China
Sensylink (矽睿科技) — AMR/TMR magnetometers
Asair (奥松) — Temperature and humidity sensors
Winsen (炜盛) — Gas sensors (CO, CH4, H2S), industrial-grade

Sourcing Tips

Three lessons from real orders, in the order we've seen them bite people:

Buy moisture-sensitive sensors factory-sealed on tape and reel — hand-soldering risks damaging the sensing element
Always request calibration certificates for medical or industrial applications
MEMS sensors have long lead times during automotive production ramps — plan 12-16 weeks ahead

IoT Module Selection Guide — Wireless connectivity for sensor devices
Wireless Connectivity Compared — BLE, LoRa, NB-IoT for IoT sensors
Power Management IC Selection Guide — Powering your sensor nodes efficiently