Which sensor are basically made of a pyroelectric sensor which can detect levels of infrared radiation?

The sensor that is fundamentally based on a pyroelectric element and designed to detect levels (more accurately, changes in levels) of infrared radiation is the Passive Infrared (PIR) sensor. These are the devices most commonly found in motion detectors used for security, lighting control, and presence sensing.

While the pyroelectric effect responds to temperature *changes* caused by IR radiation, the overall PIR sensor system is engineered specifically for this detection task. The pyroelectric material absorbs incoming IR, its temperature changes, and it generates an electrical signal. The associated electronics then amplify and process this signal. Often, PIR sensors use a differential setup (two or more sensing elements) combined with a segmented lens (like a Fresnel lens) to enhance sensitivity to movement across different zones.

Therefore, when thinking of a sensor primarily built around a pyroelectric element for detecting infrared radiation, particularly for applications like motion detectors, the PIR sensor is the quintessential example. Other devices might incorporate pyroelectric elements (like some types of flame detectors or gas sensors), but the PIR motion sensor is the most direct and widespread application where the pyroelectric sensor forms the core detection mechanism for infrared radiation changes.