emonTH -Temperature & Humidity Node

£44.39 (Inc. VAT)
£36.99 (Ex. VAT)
200.00 Grams
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The emonTH V2 is an open-source, wireless, battery powered temperature and humidity monitoring node. 

It is an easy to deploy tool for monitoring building / room temperature and humidity. Data from the emonTH is transmitted via UHF radio (433MHz) to an emonPi / emonBase web-connected base-station for logging to Emoncms for data logging, processing and graphing. Room temperature and humidity data can be used to inform a heating control system, feed into a building performance model or simply for general interest.



Temperature and humidity sensing - using the onboard Si7021 temperature and humidity sensor and (optionally) an external DS18B20 temperature sensor.


  • Easy to set-up - the unit comes pre-assembled and pre-loaded with Arduino compatible firmware. If desired the code can easily be modified using Arduino IDE or PlatformIO and uploaded using an USB to UART cable to the on-board ATmega328 microprocessor.


  • Long Battery Life - The emonTH is powered by two AA batteries which will last over 4 years. Use alkaline batteries for longest battery life or rechargable eneloops for best environmental benefit. 



  • RF node ID DIP switch Selection - Up to four RF node IDs (23,24,25 & 26) can be set via physical onboard DIP switches. See hardware wiki.



  • Microcontroller: Arduino compatible ATmega328p
  • Internal Sensor: Si7021 (internal temperature & Humidity)
  • External Sensor (OPTIONAL): DS18B20 external temperature sensor. See hardware wiki for connections
  • Power: 2 x AA from on-board holder, LTC3525 3.3V DC-DC boost converter to extend battery life
  • RF Radio: RFM69CW 433Mhz
  • Acrylic enclosure
  • 4 year+ battery life 
  • External dimensions: 71 x 71 x 27 mm


Si7021 Temperature & Humidity Sensor

  • Silicon Labs SI7021-A20-GM1R
  • Power supply 1.9V - 3.6V
  • Operating range humidity 0-80%RH; temperature -40~125 deg C
  • Accuracy humidity +-3%RH
  • Accuracy Temperature: +-0.4 degC
  • Active current: 150uA
  • Sleep current 0.06uA
  • Measurement time: 2.6ms = 10ms

Si7021 (emonTH V2) Vs. DHT22 (emonTH V1) comparison