3-phase emonTx V4 with Onboard Wi-Fi

£153.54 (Inc. VAT)
£127.95 (Ex. VAT)
250.00 Grams
Current Stock:
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This version of the emonTx V4 has a on-board ESP8266 WiFi module for direct WiFi connection (emonBase not required). Using an emonVS power supply to provide power and AC voltage sample is highly recommended for accurate monitoring. 

The ESP8266 comes pre-loaded with EmonESP which can post data to MQTT & Emoncms 


Note: the emonTx V4 3-phase supports 4-wire 3-phase systems i.e with a Neutral wire, 3-wire 3-phase systems (without a Neutral) are not supported. 


The emonTx v4 is the latest generation of OpenEnergyMonitor open source monitoring hardware, redesigned with a focus on higher accuracy, more CT channels, precision voltage sensing and a new microcontroller core. When combined with the new emonVS voltage sensor, the emonBase base-station and a selection of CT sensors, it provides an end-to-end electricity monitoring solution perfect for monitoring home consumption, solar generation, EV charging, heat pumps, battery storage or any AC electrical circuit for that matter.

The emonTx v4 is an energy monitoring transmitter unit that can monitor AC electrical active power on up to 6 separate AC circuits using non-invasive clip-on CT current sensors and the emonVs voltage sensor.

The emonVs is a combined precision voltage sensor and power supply unit designed to be used with the emonTx v4 for higher accuracy voltage measurement and a single socket or hardwire install, use a separate AC/AC adaptor is not required. 

The emonTx is designed to be used together with an emonBase web-connected base station (available as an option in this bundle). The emonBase comprises a Raspberry Pi and RF transceiver. It can be used to log data locally to the Raspberry Pi's SD card or post data to Emoncms.org.

emonTx v4 features:

  • 6x clip-on CT current sensor inputs (suitable for a range of 333mV voltage output CT sensors).
  • emonVs precision voltage sensor input.
  • Full Real/Active power measurement & continuous sampling.
  • Cumulative energy persisted on reboot.
  • The initial firmware release supports single phase monitoring only.
  • 3 pluggable terminal block inputs for DS18B20 temperature sensing, pulse counting or an analogue voltage input.
  • RJ45 socket for pulse counting and DS18B20 temperature sensors.
  • On-board USB-C to UART converter for easier programming and serial output.
  • 433 MHz radio transceiver
  • Extension header pins for use with ESP8266, ESP32, Pi Pico & Pi Zero development board extension modules
  • Wall-mount aluminium enclosure

emonVs features

  • Precision voltage sensor provides voltage signal for the emonTx v4.
  • Supports a range of mains voltages 120-240V, US, EU, UK.
  • Single phase as standard.
  • 10W Power supply can power both the emonTx v4 (via RJ11) and the emonBase (via USB-C)
  • (Please email us if you would like to buy a 3-phase capable voltage sensor in advance of the available firmware).

emonBase features

  • Raspberry Pi mini computer
  • 433Mhz RFM69CW Direct SPI adaptor board
  • High quality black aluminium enclosure designed for easy wall mounting.
  • Full local data logging and visualisation capability using emoncms.
  • Option to post data to a remote server such as emoncms.org
  • Data accessible via MQTT
  • Software support for reading from Modbus & M-BUS meters via USB


CT current sensor selection

To obtain the highest accuracy we recommend choosing CT current sensors that match the current rating of the circuit being measured. 

E.g for 16A or 20A circuits choose the 20A CT sensor, for 32A or 40A circuits choose the 50A CT sensor and so on. No damage will be done if the current in the circuit exceeds the CT rating, the output will just be 'clipped' resulting in inaccuracy.

The physical size of the CT sensors is also proportional to the current rating which makes the smaller sensors very suitable for installation inside fuseboxes / consumer units.  See individual CT current sensor product pages for more information:

The standard 3-phase firmware allocates each phase to each CT input on the emonTx4 as follows:

  • CT 1: phase 1
  • CT 2: phase 2
  • CT 3: phase 3
  • CT 4: phase 1
  • CT 5: phase 2
  • CT 6: phase 3

Note: The emonTx V4 requires voltage output CT sensors, it is NOT compatible with the old current output YHDC (blue) 100A CT sensors.


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