The “over temperature” logic controller keeps the vessel’s outer wall temperature from getting extremely hot and, in turn, going beyond the internal set temperature of the sample vessel. For example, if you have an internal vessel temperature set to 40oC, you would set the external wall temperature or “over temperature” controller to 45oC. In this way, you maintain the internal temperature at 40oC without exceeding the desired temperature. Keep in mind you are heating a very large metal mass in the sample vessel. There is a certain amount of histolysis of heat through the vessel wall. To maintain accurate temperature control, management of both the internal vessel temperature and external wall temperature is the best solution.