The development of temperature sensor
The temperature sensor is an early developed and widely used type of sensor. Since Galileo invented the thermometer in the early 17th century, people have been measuring temperature, and the sensor that truly converts temperature into an electrical signal is the thermocouple sensor invented by German physicist Seebeck in 1821.
With the continuous development of technology and the increasing demand for measurement and automation technology, the development of temperature sensor has gone through the following three stages: traditional discrete temperature sensors (including sensitive elements), analog integrated temperature sensors/controller, and intelligent temperature sensors. Currently, new types of temperature sensors are developing towards digitalization, intelligence, and networking from analog and integrated types.
1. Discrete Temperature Sensor
Thermocouple sensors are a traditional type of discrete sensor and are the most widely used temperature sensors in industrial measurement. Its working principle is based on the Seebeck effect in physics, which means that an electromotive force corresponding to the temperature difference is generated in the circuit composed of two metal wires if their junctions are maintained at different temperatures. The thermocouple has a simple structure, a wide temperature range, a fast response, accurate measurement, good reproducibility, and can measure micro-area temperatures with fine wires, and it does not require a power supply.
2. Integrated Temperature Sensor/Controller
Analog Integrated Temperature Sensor
Integrated sensors are made using silicon semiconductor integration technology, and are also called silicon sensors or single-chip integrated temperature sensors. Analog integrated temperature sensors were introduced in the 1980s. It is a special IC that integrates temperature sensors on a chip and can complete temperature measurement and analog signal output functions. The main features of analog integrated temperature sensors are single function (only temperature measurement), small measurement error, low price, fast response, long transmission distance, small size, low power consumption, etc. They are suitable for long-distance temperature measurement and control, do not require nonlinear calibration, and have simple peripheral circuits. They are currently the most commonly used type of integrated sensor both domestically and internationally.
Analog Integrated Temperature Controller
Analog integrated temperature controllers mainly include temperature control switches and programmable temperature controllers. Some enhanced integrated temperature controllers also include A/D converters and fixed programs, which have some similarities with intelligent temperature sensors. However, it is a self-contained system and does not work under the control of a microprocessor, which is the main difference between the two.
3. Smart Temperature Sensor
The smart temperature sensor (also known as a digital temperature sensor) emerged in the mid-1990s. It is a product of microelectronics technology, computer technology, and automatic test equipment (ATE). Currently, various series of smart temperature sensor products have been developed internationally. Smart temperature sensors contain a temperature sensor, A/D converter, signal processor, memory (or register), and interface circuitry internally. Some products also include multi-channel selectors, central controllers (CPU), random-access memory (RAM), and read-only memory (ROM). The feature of a smart temperature sensor is its ability to output temperature data and related temperature control parameters, and adapt to various microcontrollers (MCU); it implements testing functions through software on the hardware basis, and its level of intelligence also depends on the software development level.
After entering the 21st century, smart temperature sensors are rapidly developing towards high precision, multi-functionality, bus standardization, high reliability and safety, developing virtual and network sensors, and researching single-chip temperature measurement systems. Along with a series of policies and measures favorable to the development of the temperature sensor industry, the industry will embrace great development opportunities in the future.