A Holder of temperature sensitive elements

A Holder of temperature sensitive elements can best be used in an experiment of a flow in liquids, where it would be very difficult for a teacher to perform the experiment by himself. A teacher has to be able to hold the holder with a test tube and simultaneously set two temperature sensitive elements in the right height to be able to see a temperature difference, which is of interest to us. The teacher would usually have to pick out one of the students to help him with the experiment. This way