The Android platform provides four sensors that let you monitor various environmental properties.
You can use these sensors to monitor relative ambient humidity, illuminance, ambient pressure, and
ambient temperature near an Android-powered device. All four environment sensors are hardware-based
and are available only if a device manufacturer has built them into a device. With the exception of
the light sensor, which most device manufacturers use to control screen brightness, environment
sensors are not always available on devices. Because of this, it's particularly important that you
verify at runtime whether an environment sensor exists before you attempt to acquire data from
it.

Unlike most motion sensors and position sensors, which return a multi-dimensional array of sensor
values for each [SensorEvent](https://developer.android.com/reference/android/hardware/SensorEvent), environment sensors return a single sensor
value for each data event. For example, the temperature in °C or the pressure in hPa.
Also, unlike motion sensors and position sensors, which often require high-pass or low-pass
filtering, environment sensors do not typically require any data filtering or data processing. Table
1 provides a summary of the environment sensors that are supported on the Android platform.


**Table 1.** Environment sensors that are supported on the Android platform.

| Sensor | Sensor event data | Units of measure | Data description |
|---|---|---|---|
| [TYPE_AMBIENT_TEMPERATURE](https://developer.android.com/reference/android/hardware/Sensor#TYPE_AMBIENT_TEMPERATURE) | `event.values[0]` | °C | Ambient air temperature. |
| [TYPE_LIGHT](https://developer.android.com/reference/android/hardware/Sensor#TYPE_LIGHT) | `event.values[0]` | lx | Illuminance. |
| [TYPE_PRESSURE](https://developer.android.com/reference/android/hardware/Sensor#TYPE_PRESSURE) | `event.values[0]` | hPa or mbar | Ambient air pressure. |
| [TYPE_RELATIVE_HUMIDITY](https://developer.android.com/reference/android/hardware/Sensor#TYPE_RELATIVE_HUMIDITY) | `event.values[0]` | % | Ambient relative humidity. |
| [TYPE_TEMPERATURE](https://developer.android.com/reference/android/hardware/Sensor#TYPE_TEMPERATURE) | `event.values[0]` | °C | Device temperature.^1^ |

^**1**^ Implementations vary from device to
device. This sensor was deprecated in Android 4.0 (API Level 14).

## Use the light, pressure, and temperature sensors

The raw data you acquire from the light, pressure, and temperature sensors usually requires no
calibration, filtering, or modification, which makes them some of the easiest sensors to use. To
acquire data from these sensors you first create an instance of the [SensorManager](https://developer.android.com/reference/android/hardware/SensorManager) class, which you can use to get an instance of a physical sensor.
Then you register a sensor listener in the [onResume()](https://developer.android.com/reference/android/app/Activity#onResume()) method, and start handling incoming sensor data in the [onSensorChanged()](https://developer.android.com/reference/android/hardware/SensorEventListener#onSensorChanged(android.hardware.SensorEvent)) callback method. The
following code shows you how to do this:  

### Kotlin

```kotlin
class SensorActivity : Activity(), SensorEventListener {

    private lateinit var sensorManager: SensorManager
    private var pressure: Sensor? = null

    public override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.main)

        // Get an instance of the sensor service, and use that to get an instance of
        // a particular sensor.
        sensorManager = getSystemService(Context.SENSOR_SERVICE) as SensorManager
        pressure = sensorManager.getDefaultSensor(Sensor.TYPE_PRESSURE)
    }

    override fun onAccuracyChanged(sensor: Sensor, accuracy: Int) {
        // Do something here if sensor accuracy changes.
    }

    override fun onSensorChanged(event: SensorEvent) {
        val millibarsOfPressure = event.values[0]
        // Do something with this sensor data.
    }

    override fun onResume() {
        // Register a listener for the sensor.
        super.onResume()
        sensorManager.registerListener(this, pressure, SensorManager.SENSOR_DELAY_NORMAL)
    }

    override fun onPause() {
        // Be sure to unregister the sensor when the activity pauses.
        super.onPause()
        sensorManager.unregisterListener(this)
    }
}
```

### Java

```java
public class SensorActivity extends Activity implements SensorEventListener {
    private SensorManager sensorManager;
    private Sensor pressure;

    @Override
    public final void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.main);

      // Get an instance of the sensor service, and use that to get an instance of
      // a particular sensor.
      sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
      pressure = sensorManager.getDefaultSensor(Sensor.TYPE_PRESSURE);
    }

    @Override
    public final void onAccuracyChanged(Sensor sensor, int accuracy) {
      // Do something here if sensor accuracy changes.
    }

    @Override
    public final void onSensorChanged(SensorEvent event) {
      float millibarsOfPressure = event.values[0];
      // Do something with this sensor data.
    }

    @Override
    protected void onResume() {
      // Register a listener for the sensor.
      super.onResume();
      sensorManager.registerListener(this, pressure, SensorManager.SENSOR_DELAY_NORMAL);
    }

    @Override
    protected void onPause() {
      // Be sure to unregister the sensor when the activity pauses.
      super.onPause();
      sensorManager.unregisterListener(this);
    }
}
```

You must always include implementations of both the [onAccuracyChanged()](https://developer.android.com/reference/android/hardware/SensorEventListener#onAccuracyChanged(android.hardware.Sensor, int)) and [onSensorChanged()](https://developer.android.com/reference/android/hardware/SensorEventListener#onSensorChanged(android.hardware.SensorEvent)) callback methods. Also, be
sure that you always unregister a sensor when an activity pauses. This prevents a sensor from
continually sensing data and draining the battery.

## Use the humidity sensor

You can acquire raw relative humidity data by using the humidity sensor the same way that you use
the light, pressure, and temperature sensors. However, if a device has both a humidity sensor
([TYPE_RELATIVE_HUMIDITY](https://developer.android.com/reference/android/hardware/Sensor#TYPE_RELATIVE_HUMIDITY)) and a temperature sensor ([TYPE_AMBIENT_TEMPERATURE](https://developer.android.com/reference/android/hardware/Sensor#TYPE_AMBIENT_TEMPERATURE)) you can use these two data streams to calculate
the dew point and the absolute humidity.

#### Dew point

The dew point is the temperature at which a given volume of air must be cooled, at constant
barometric pressure, for water vapor to condense into water. The following equation shows how you
can calculate the dew point:
![t_d(t,RH) = Tn · (ln(RH/100) + m·t/(T_n+t
))/(m - \[ln(RH/100%) + m·t/(T_n+t)\])](https://developer.android.com/static/images/guide/topics/sensors/dew_point.png)

Where,

- t~d~ = dew point temperature in degrees C
- t = actual temperature in degrees C
- RH = actual relative humidity in percent (%)
- m = 17.62
- T~n~ = 243.12

#### Absolute humidity

The absolute humidity is the mass of water vapor in a given volume of dry air. Absolute
humidity is measured in grams/meter^3^. The following equation shows how you
can calculate the absolute humidity:
![d_v(t,RH) = (RH/100) · A · exp(m·
t/(T_n+t)/(273.15 + t)](https://developer.android.com/static/images/guide/topics/sensors/absolute_humidity.png)

Where,

- d~v~ = absolute humidity in grams/meter^3^
- t = actual temperature in degrees C
- RH = actual relative humidity in percent (%)
- m = 17.62
- T~n~ = 243.12 degrees C
- A = 6.112 hPa

### You should also read

- [Sensors](https://developer.android.com/guide/topics/sensors)
- [Sensors Overview](https://developer.android.com/guide/topics/sensors/sensors_overview)
- [Position Sensors](https://developer.android.com/guide/topics/sensors/sensors_position)
- [Motion Sensors](https://developer.android.com/guide/topics/sensors/sensors_motion)