Whether you think your child has a fever or you’re wondering if your baby’s food is at the right temperature, a digital thermometer is the right device for the answers you need. But how does a digital thermometer work? It may be simpler than you think. While every company has its proprietary secrets, most digital thermometers work on the same principles – and all use similar technology. The difference is in the way the devices are designed and constructed and the quality of the components used. How Digital Thermometers Work Digital thermometers contain a small computing mechanism and a resistor. A change in temperature causes the sensor to notice a change in resistance. The computer converts the difference in resistance into a difference in temperature and offers a digital readout in degrees.