Clinical thermometers have the practical difficulty of disposing of the mercury while it is breaking down. Mercury is a toxic substance, so it is needed to be disposed of properly and safely. To overcome this situation, nowadays, Digital thermometers are used to measure body temperature in clinics.
Fig. - Digital Thermometer
Digital thermometers work on the principle that the electrical resistance of the material changes with temperature. Digital thermometers are different to conventional thermometers, such as liquid-filled and bimetallic thermometers in that they need a sensor. These sensors produce a resistance, current or voltage in reaction to a change in temperature. These changes are referred to as analogue output signals, and it is converted to digital to make it easy to visible.
Infrared thermometers are typically used to measure the temperatures that are necessary to be measured from a distance. They give accurate temperatures without ever having to touch the objects that you are measuring (even when your object is in motion).
Fig. - Infrared Thermometer