In this way, it is possible to detect the temperature of the medium during the heating with only one temperature measuring device at different intervals from the heating plate. Since the heating generally starts from the bottom on account of the heating plate arranged underneath the container or beaker in the usage position and accordingly the temperature within the medium decreases from bottom to top, it is possible to identify a temperature stratification or a temperature distribution within the container especially during the heating of the medium, but also in the further operation, with the help of the temperature measuring device. [...]it is possible to control and/or regulate a stirring process, which can help homogenize the temperature within the medium, in dependence on the detected temperature distribution. [...]even in the case of stirring magnets which have a length corresponding to the diameter of the container or beaker a collision of the stirring magnet rotating in the beaker or container during the operation of the magnetic stirrer with the temperature measuring device located in its position of use can be avoided. On a rod-shaped thermometer the at least three temperature sensors can be arranged with sufficient vertical spacing from each other. [...]it is possible with a correspondingly long rod-shaped thermometer to identify or monitor a temperature distribution and also the level of a medium over a correspondingly large vertical region. [...]it is possible to connect the temperature measuring device to a display device for the displaying of the detected measurement values...