RS485 Temperature and Humidity Sensor

This temperature and humidity sensor from DFRobot sits in an aluminium tube and outputs its values as an RS485 signal with the MODBUS RTU protocol. According to DFRobot, RS485 allows lines up to 1200 m and several sensors on one line. It measures -40 °C to 120 °C and 0 to 99.9 % RH and is supplied with 12 V to 36 V DC.

Important: According to IP34 the sensor is only protected against splashing water. Do not immerse it in water or wet soil and do not rinse it. Outdoors and in greenhouses it needs a rain or weather shield. DFRobot recommends mounting it with the tip pointing vertically downwards and warns against condensation and heavy dust.

Note: The sensor cannot be connected directly to a microcontroller or a USB port. For a PC a USB to RS485 converter is needed, for Arduino or ESP32 an RS485 shield or module. The 5 V of an Arduino are not sufficient for the supply.

Recommended Accessories:

Features:

RS485 with MODBUS RTU, 9600 baud by default
Line length up to 1200 m according to DFRobot
Temperature -40 °C to 120 °C, ±0.3 °C at 25 °C
Humidity 0 to 99.9 % RH, ±2 % RH at 25 °C
Measurement every 3 seconds
Aluminium housing with breathable membrane

Application Examples:

Greenhouse with weather shield
Stores and warehouses
Heating, ventilation and air conditioning (HVAC)
Building automation over long lines

Documentation:

Technical Data:

Manufacturer: DFRobot
Manufacturer SKU: SEN0438
Temperature: -40 °C to 120 °C, ±0.3 °C at 25 °C, resolution 0.1 °C
Humidity: 0 to 99.9 % RH, ±2 % RH at 25 °C, resolution 1 % RH
Long-term drift: temperature below 0.1 °C per year, humidity below 0.5 % RH per year
Measuring interval: 3 s
Supply: 12 V to 36 V DC
Current consumption: up to 20 mA
Output: RS485, MODBUS RTU protocol
Baud rate: 9600 (default)
Wiring: yellow RS485 A, white RS485 B, red supply, black GND
Protection class: IP34
Dimensions: length 200 mm, diameter 15.7 mm
Weight: 110 g