source: Support/Device-Sensors.md

## Device Sensors 

LibreNMS has a standard for device sensors they are split into categories.
This doc is to help users understand device sensors in general, if you need help with developing sensors for a device please see the Contributing + Developing section. 

### Health Sensors

The High and Low values of these sensors can be edited in Web UI by going to the device settings -> Health. There you can set your own custom
High and Low values. List of these sensors can be found here [Link](../Developing/os/Health-Information.md)

**Note** Some values are defined by the manufactures and others are auto calculated when you add the device into librenms. Keep in mind every environment is different and may require user input.


### Wireless Sensors

Some Wireless have  High and Low values of these sensors can be edited in Web UI by going to the device settings -> Wireless Sensors There you can set your own custom High and Low values. List of these sensors can be found here [Link](../Developing/os/Wireless-Sensors.md)

**Note** Some values are defined by the manufactures and others are auto calculated when you add the device into librenms. Keep in mind every environment is different and may require user input.

### State Sensors

Return states of device entries sensors states. For example. 

Drive Status, Memory Status, Power Supply Status. 

```
0 = OK
1 = Warning
2 = Critical
3 = Unknown
```

### Alerting Sensors

These alert rules can be found inside the Alert Rules Collection. The alert rules below are
the default alert rules, there are more device-specific alert rules in the alerts collection. 

**Sensor Over Limit Alert Rule:**  Will alert on any sensor value that is over the limit.

**Sensor Under Limit Alert Rule:** Will alert on any sensor value that is under the limit.

**Remember** you can set these limits inside device settings in the Web UI.

**State Sensor Critical:** Will alert on any state that returns critical = 2

**State Sensor Warning:** Will alert on any state that returns warning = 1

**Wireless Sensor Over Limit Alert Rule:** Will Alert on sensors that listed in device settings under Wireless.

**Wireless Sensor Under Limit Alert Rule:** Will Alert on sensors that listed in device settings under Wireless.
