If digital thermometers do not contain mercury, how does it measure temperature?

A digital thermometer doesn't require mercury to read temperature. There is an electronic heat sensor and an electronic circuit to read the temperature detected by the sensor. In a mercury thermometer the length of the mercury within the capillary increases or decreases when the temperature increases or decreases. While in a digital thermometer no such thermal phenomenon occurs. The sensor at the tip of the thermometer picks up heat from the body whose temperature is to be detected and it receives the heat until its temperature becomes equal to the temperature of the body. The display of the thermometer shows the temperature read by the thermometer.