> For the complete documentation index, see [llms.txt](https://docs.rapt.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.rapt.io/equipment/rapt-laser-level-sensor/laser-array-guide.md). # Laser Array Guide When using the RAPT Lasrer Level Sensor, to get the most reliable reading from the surface of the liquid/solid it’s best that the *entire* laser array falls onto the *surface* of the product being measured (rather than the wall of the vessel). The image below shows how the laser array fires out from the base of the unit.

RAPT Laser Level Sensor - Array Visualisation

For unusually shaped vessels or vessels that are not a standard cylinder, such as conical tanks, the laser will start to give less accurate readings as the the majority of the laser falls onto the *walls* of the conical tank rather than onto the liquid itself. This will generally happen as the liquid level is quite low in the vessel. For example, in the BrewBuilt 144L conical fermenter the sensor will give poor accuracy in the last 5L of tank volume and may be undetectable.