Richard type thermograph, belonged to De Marchi. 1930s.

The thermograph measures and records the air temperature. His sensor is the Bourdon tube, placed in the cage outside the recording system. This sensor is a C shaped tube filled with a liquid changing volume with changes of temperature, thus increasing or decreasing the curvature of C shaped tube. One end of the Bourdon tube operates a lever, moving a long needle with a writing tip ad the edge. The writing tip writes on a paper strip with temperature-time coordinates printed over. The paper strip is wrapped around a cylinder rotating by a clockwork and running for one week.