For measuring body temperature we use clinical thermometer (fig i)since its range is 35 to 42 degree Celsius which can be use to get the temperature of fever body of human being then it was replaced by digital thermometer (fig iii )since it was error free and also there was no risk of mercury as it is toxic and can even lead to death.

Fig ii is the clinical thermometer which is used to measure the temperature of bodies having a higher temperature which is out of range of a normal thermometer.