Smart Sensor Systems

7

Smart Temperature Sensors andTemperature-Sensor Systems

Gerard C.M. Meijer

7.1 Introduction¹

In smart sensors, sensing elements are combined with sensor-interface electronics on a single chip. Such a combination can be very favorable in terms of reliability, standardization of the output signal, accuracy, overall calibration, etc.. Because in some aspects the technologies for fabricating sensors and electronics are incompatible, it is not easy to make sensors smart. For instance, a problem for a smart chemical sensor is that on the one hand it should allow a good electrochemical interaction with its environment, while on the other hand the electronic circuit should be resistant against these chemicals. In a similar way, it is not easy to fabricate a smart temperature sensor for measuring very high temperatures (for instance > 300 °C), as this requires the use of special IC technologies. However, such technologies are not needed for smart temperature sensors measuring in the intermediate temperature range of –50 °C to + 180 °C. This is because, within this temperature range, the sensors can work for a long time with high accuracy and high reliability. Moreover, the sensor chip can be hermetically sealed with a metal encapsulation and yet, because of the high thermal conductivity of the encapsulation, there can be a good thermal interaction between the chip and its thermal environment. For these reasons smart temperature sensors are among the oldest types of smart sensors ever ...