Industrial glass thermometers do not drift. They keep their once-defined accuracy for life. Only the mechanical destruction of the glass insert or a separation of the thermometric filling leads to a failure of the correct measurement. However, both are visible to the naked eye and can be corrected by replacing the glass insert or reuniting the thread.
Nevertheless, there are always attempts to calibrate mechanical measuring instruments. However, for several reasons, this is not an easy thing to do.
According to the calibration instructions for dry block temperature calibratorsDKD R5-4 // EA10-/13 // EURAMET CG13, the homogeneous zone, i.e. the range in which the temperature sensor should be calibrated is indicated as 40 mm. This homogeneous zone is usually located at the lower end of the block of the calibrator.