To calibrate short temperature sensors is always a challenge. The higher temperature you want to calibrate, the more difficult it becomes. The problem is the heat loss in the top of the calibrator. The temperature at the top of a calibrator is very much influenced from the ambient temperature. To make sure to overcome that problem two things have to be done: the temperature at the top of the calibrator will have to only be influenced by the ambient by a minimum and it should be possible to measure the temperature at the top of the calibrator.