> For the complete documentation index, see [llms.txt](https://docs.skysens.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.skysens.io/sources/virtual-sensor.md). # Virtual Sensor Virtual Sensors are virtual assets explained in [asset types](/asset/asset-types.md#virtual-assets). It creates an option to you create a source without a physical device representation. There is three type of virtual sensor: Virtual Value, Virtual Form, Virtual Simulation. Virtual Value is often used when you need a empty sensor that you can set output of a rule without interacting with physical device data. Virtual Form is often used when you want a simple placeholder sensors that store constant data. You can enter your constants or variable within a simple form. Simulation is a virtual representation of a physical device or a situation with some custom configurations.