A device is a single piece of hardware in the Tempest system. Each device in the Tempest system must belong to a station. A device observation returns data for each sensor of the device.
A station is made up of one or more devices in the same location. A station observation returns a federated observation for all device sensors that are a part of the station. Since stations can have multiple devices with the same sensor type, station owners can designate which device sensor is the primary sensor that will be included as part of the station observation. For example, if a station has two devices and each one has a temperature sensor, the station observation will only return one temperature value and it will be the one from the device the user designated as the primary temperature device.
In most cases, you should use station observations. Station observations ensure you are getting data back from the primary sensors for each station. Device observations should be used only if you know that you want data back from a specific device regardless of the user's primary sensor designations.
Currently, the WebSocket endpoint only returns device observations.