Pyroelectricity can be described as the ability of certain materials to generate a temporary voltage when they are heated or cooled. The pyroelectric sensor uses the pyroelectric effect of ceramics to detect infrared energy from a human body. It is important to note that the sensor detects a heat source if there is more than a 4°C temperature difference from ambient temperature. This means it can also detect spot light and sunshine if there is enough of a temperature difference.