This is an explosion-proof float switch in a stainless steel container. These containers are equipped with defined holes on the bottom of the vessel. If the water level rises at the installation site, the float switch triggers, the controller records a high water message.
In order to ensure that the floodwater report is working without disturbance, in the case of quiescent areas or at weekends, this can be checked externally. For this, water can be admitted into the tank with float switch via a switching valve in another stainless steel box. The water flows into the container faster than it can flow out through the holes. This switches the float switch and the test has been successful. The valve is closed and the water can drain out of the tank.
This unit is designed to protect expensive equipment in areas where people are not always on site.