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EZO sensors~

EZO is a series of chemical sensors provided by Atlas Scientific


All EZO devices must operate under the I2C mode to be compatible with Tasmota. One of the easiest way to achieve this is to short SDA/Tx to PGND while powering the device through VCC & GND. For more details, see Instructables.

Tasmota will automatically detect any new device that has an I2C bus address between 0x61-0x70 (which covers the default address range of all EZO devices). Tasmota supports any multiple of EZO devices (up to 16 of any kind). When more than one device is detected, the devices will be indexed starting at index 1 (ex: EZO-1) and ordered by their I2C address. If only one EZO device is connected, there will be no indexing of them. You may change the address of your device by sending an I2C command to the device. For example, to change the address of a single EZOpH sensor, the following command can be issued in the console:

Sensor78 I2C,100

Specific details about the list of commands available for your EZO device can be found in the device-specific datasheet on the Atlas Scientific's website. In order to individually address a single EZO sensor when more than one is detected, the index must be specified on the command by appending "-#" to the command:

Sensor78-2 I2C,101


Many EZO devices require calibration in order to accurately report values. Calibration can be easily achieved by issuing the appropriate commands and following the instructions in the EZO datasheets. One easy way to achieve this is to put the sensor in the baseline environement and use the web interface to see when the value stabilizes. Once it does, visit the console and issue the device-specific calibration command.


Currently, Tasmota samples the sensor information at the rate of 1Hz (1 sample/second) irrespective of the EZO device.

Some EZO devices support reporting different units. For example EZO-RTD supports reading the temperature in °C, °K, or °F. In order to save memory, Tasmota will only be able reading the default format (ie: °C). If you wish to see the value in another format, you can use Tasmota's ability to display Farenheit to do the conversion for you. For conversions that are not supported by Tasmota, you may use OpenHab, Home Assistant or any other system in conjunction with MQTT to do the cnoversion. In every case, there exists a simple formula that will allow you to convert from one format to another and the EZO device are merely utilizing that formula to return the value. It's important to make sure that the default units are used. If that's not the case, Tasmota will simply assume that the default units are used and the number will seem drastically wrong.

Some device supports the output of multiple diffrent sensors in one single EZO devices. One example of this is the EZO-HUM which supports outputing the humidity as well as the temperature. By default, only the humidity is enabled, but a command can be sent to enable the temperature as well. In that case, Tasmota does support reading the additional sensor provided that the command enables its output.

Some readings can be made more precise by specifying additional parameters. The most common one is temperature. For example, the EZO-pH sensor can return more accurate values if it compensates for the temperature. At this point in time, Tasmota does not support reading sensor data which compensates with any other sensor's data. That said, these are typically well-established equations that will allow you to convert the existing reading and adjust it based on the reading from the other sensor. A simple Google search can be done to understand how to compensate in each case.

Sleep mode for EZO devices is currently NOT supported by Tasmota.

Build Configuration~

By default, the EZO sensor is NOT built in the Tasmota binary. The Tasmota web build interface can be used to produce the proper binary. The following #define must be enabled in order to compile the following supported sensors:

At this point in time, the following EZO sensors are supported:

Required build #define Sensor ID Sensor Name
USE_EZODO EZO-D.O. Disolved Oxygen
USE_EZOORP EZO-ORP Oxygen Reduction Potential
USE_EZOEC EZO-EC Electric Conductivity
USE_EZOCO2 EZO-CO2 Carbon Dioxyde (gas)
USE_EZOO2 EZO-O2 Oxygen (gas)