Pneumatic temperature difference switch - has contacts joined by mercury droplet in U=tube joining two sensors, esp. for solar installation

摘要

The switch has two sensors (1,6) connected together by an insulating tube (4) filled with gas (pref. air). The tube is U-shaped and has a mercury droplet (5) at its lowest point. The mercury droplet connects two contacts (7,8) in an electrical circuit. One contact is in the left-hand limb and the other in the right-hand limb of the tube. One sensor (1) is located in a cell (2) mounted on a window (3) and heated by solar radiation passing through the window. This sensor is a bellows (pref. made of metal) whose volume can be changed by a setting screw (9). The second sensor (6) consists of a closed chamber.