3.4 KiB
title, sidebar_label
| title | sidebar_label |
|---|---|
| Sensor Entity | Sensor |
A sensor is a read-only entity that provides some information. Information has a value and optionally, a unit of measurement.
Properties
:::tip
Properties should always only return information from memory and not do I/O (like network requests). Implement update() or async_update() to fetch data.
:::
| Name | Type | Default | Description |
|---|---|---|---|
| state | string | Required | The value of the sensor. |
| device_class | string | None |
Type of sensor. |
| last_reset | datetime.datetime |
None |
The time when an accumulating sensor such as an electricity usage meter, gas meter, water meter etc. was initialized. If the time of initialization is unknown and the meter will never reset, set to UNIX epoch 0: homeassistant.util.dt.utc_from_timestamp(0). Note that the datetime.datetime returned by the last_reset property will be converted to an ISO 8601-formatted string when the entity's state attributes are updated. When changing last_reset, the state must be a valid number. |
| state_class | string | None |
Type of state. |
| unit_of_measurement | string | None |
The unit of measurement that the sensor is expressed in. |
Available device classes
If specifying a device class, your sensor entity will need to also return the correct unit of measurement.
| Type | Unit | Description |
|---|---|---|
| battery | % | % of battery that is left. |
| carbon_dioxide | ppm | parts per million of carbon dioxide concentration |
| carbon_monoxide | ppm | parts per million of carbon monoxide concentration |
| humidity | % | % of humidity in the air. |
| illuminance | lx/lm | Light level. |
| signal_strength | dB/dBm | Signal strength. |
| temperature | °C/°F | Temperature. |
| timestamp | ISO8601 | Timestamp. |
| power | W,kW | Power. |
| pressure | hPa,mbar | Pressure. |
| current | A | Current. |
| energy | Wh,kWh | Energy. |
| power_factor | % | Power Factor. |
| voltage | V | Voltage. |
| monetary | ISO 4217 | Monetary value with a currency |
Available state classes
| Type | Description |
|---|---|
| measurement | The state represents a measurement in present time, not a historical aggregation such as statistics or a prediction of the future. Examples of what should be classified measurement are: current temperature, accumulated energy consumption, accumulated cost. Exampled of what should not be classified as measurement: Forecasted temperature for tomorrow, yesterday's energy consumption or anything else that doesn't include the current measurement. |
Long-term Statistics
Home Assistant has support for storing sensors as long-term statistics if the entity has the right properties. A requirement to opt-in for statistics is that the sensor has state_class set to measurement. That means that the current value represents the current value.
Metered entities
Metered entities have a value that keeps increasing until reset, like energy consumption or production. To have Home Assistant track this entity, you need to include a last_reset property.
Home Assistant will track the growth over the statistics period for metered entities.
Value entities
Home Assistant tracks the min, max and mean value during the statistics period.
All sensors with a unit of measurement of % are automatically tracked. Other entities opt-in based on their device_class.