Smart Temperature Sensors and Temperature‐Sensor Systems

Abstract

Abstract For temperature sensing in smart sensors and microelectromechanical systems (MEMS), the most commonly used elements are transistors, thermocouples, and thermopiles because these elements can be implemented with integrated circuit (IC) technology. At the system level, also other sensor elements are used. A comparison between different types of sensing elements is presented. For the temperature range of −55 to 150°C, bipolar junction transistors are very suited to be applied as temperature sensors because they can be fabricated in almost any standard IC technology, together with other circuitry. With similar circuits, bandgap voltage references can be made, which enables doing ratiometric measurements, where temperature-sensitive voltages are compared with an intrinsic reference voltage. In complementary metal-oxide semiconductor (CMOS) technology, component matching is poor. Yet, when using CMOS analog circuits, a very high precision can be achieved by using error-reduction techniques, such as dynamic element matching and chopping . These methods have been applied in a smart temperature sensor with a duty cycle modulated output signal, which is presented as case study. Even with a very low energy consumption, a high precision is achieved.