Buy in Shop # Overview The emonTH V2 is an open-source, wireless, battery-powered temperature and humidity monitoring node. Data from the emonTH is transmitted via wireless RF (433MHz) to an emonPi / emonBase web-connected base-station for logging to Emoncms for data logging, processing and graphing. The emonTH V2 features a [Silicon Labs Si7021](https://www.silabs.com/Support%20Documents%2FTechnicalDocs%2FSi7021-A20.pdf) temperature and humidity sensor instead of the DHT22 sensor. The Si7021 is more accurate and significantly (2000 times!) lower power then the DHT22. This increases the emonTH battery life; from 10 months to several years. The Si7021 is also much smaller than the DHT22. ![emonTH V2](img/emonth2.png) The Si7021 sensor can be seen in the top right-hand corner of the PCB. The white film on top of the sensor is a dust film and should not be removed. The dust film is factory fitted and will protect the sensor from dust and air contaminants. ![emonTH V2](img/emonth_green.png) As with all our hardware units the emonTH V2 is fully open-source and manufactured locally in North Wales, UK using non-conflict materials lead-free processes. **emonTH V2 Features** - Wireless temperature & humidity monitoring node - Communicates with emonPi & emonBase via RF (433Mhz) - 1yr+ battery life (2 x AA not included) - Up to 4x emonTH can communicate to a single emonPi* - Internal temperature & humidity + optional external probe - Optional pulse sensor input \* *More than 4x emonTH units can be connected to a single emonPi / emonBase with manual change of RF nodeID. This can be done via [serial node ID config](https://community.openenergymonitor.org/t/emontx-emonth-configure-rf-settings-via-serial-released-fw-v2-6-v3-2/2064?u=glyn.hudson)* - 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 onboard holder, LTC3525 3.3V DC-DC boost converter to extend battery life - RF Radio: RFM69CW 433Mhz **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 [See DHT22 VS Si7021 technical comparison table](https://github.com/openenergymonitor/emonth2/tree/master/sensor)