What is a temperature sensor? Structure and principle of operation

In the context of a growing industry, temperature sensors have become an integral part, playing an important role in ensuring the production process and machine operation take place efficiently and safely. Let’s learn about what is a temperature sensor with RX Tradex? The structure of the principle of operation of the infrared sensor in the article below. 

1. What is a temperature sensor?

A temperature sensor is a specialized device used to measure and record the temperature of the surrounding environment or of a specific object. With high accuracy superior to conventional temperature measurement methods, temperature sensors are capable of detecting and responding instantly when an object’s temperature changes. This device converts the temperature change into an electrical or other signal, then processes and communicates the temperature result to the user quickly and accurately.

2. Structure and principle of operation

2.1. Structure of the temperature sensor

The temperature sensor has a main construction of two different metal conductors, each of which is attached to the hot end and the cold end. In addition, the inside of the temperature sensor is also composed of many other auxiliary components such as:

• Sensor unit: This part is what determines the accuracy of the entire device. It is placed inside the protective case after it has been connected to the connector. This is where the transformation of temperature into an electrical signal takes place.
• Connecting conductors: The sensor can be connected by 2, 3 or 4 conductors. The material of the conductor is selected based on the conditions of use of the gauge, which ensures durability and accuracy during signal transmission.
• Ceramic insulating material: Plays the role of insulation, prevents short circuits and ensures insulation between wires connected to the protective housing. Ceramic insulating material ensures the safety and stability of the device.
• Filler: The filler is usually fine alumina powder, which is dried and vibrated to fill any gaps in the sensor. This substance helps protect the sensor from vibration and mechanical effects.
• Protective cover: Responsible for protecting the sensor unit and connecting wires inside. It is made from sturdy materials, suitable for use conditions and sensor size. In some cases, the protective cover may be covered with additional layers for added protection.
• Connector: Usually made of an insulating material such as ceramic, containing circuit boards, allowing a resistive connection. When necessary, converters with current strengths from 4 to 20mA can be installed instead of terminal panels, making signal transmission more flexible and efficient.

2.2. The principle of operation of the temperature sensor

The temperature sensor works on the principle of dependence on the characteristics of the heat source sensor, which is influenced by external factors. When in use, the sensor will sense the temperature change of the object to be measured and generate a corresponding signal. This signal is then converted into an electrical signal and sent to the processing circuit. The signal processing unit will decode the signal into a specific temperature value and display the result on the screen so that the user can easily monitor.

There are two main principles used to measure and record changes in temperature:

• Resistance Temperature Detector (RTD): This type of RTD sensor usually uses conductive materials such as platina. A platina wire is coiled into threads and connected to an electrical circuit. As the temperature changes, the impedance of the platina wire also transforms in a specific way. This causes a change in the current passing through the sensor, from which through the electrical circuit we can calculate the corresponding temperature value.
• Thermistor principle: A thermistor is a type of sensor that uses a material with electrical impedance that varies with temperature. As the temperature changes, the thermistor’s impedance changes dramatically. This sensor is usually built into the electrical circuit, and through the change of the current passing through it, we can determine the corresponding temperature value.

3. Types of temperature sensors

Currently, there are many types of temperature sensors on the market, used to serve many different purposes and fields. Some popular types of temperature sensors today can be mentioned as:

• Resistance Temperature Detectors (RTDs): Use the principle of changing the resistance of materials to measure temperature. Often use materials such as platina (PT100, PT1000) or nickel (Ni100, Ni1000) with high precision and stability. Popular in industry, HVAC, and scientific research.
• Thermocouple: Measures high temperature levels with good durability. It works on the Seebeck effect to create a potential when the temperature changes. Popular in industry and research due to its reliability and wide temperature resistance.
• Metal oxide resistance (Thermistor): Uses the resistance properties of metal oxide to measure temperature. Change the nonlinear resistance as the temperature changes. Applied in temperature control and electronic systems due to its high durability and low cost.
• Semiconductor thermal sensor (Diode, IC): Made from semiconductors such as Diode, Transistor, IC and works based on the degree of polarization of the P-N layers linear to the ambient temperature. High accuracy and stability, used in the air environment and in temperature instrumentation.
• Pyrometer: Measures the amount of thermal radiation emitted by objects instead of direct contact. Suitable for temperature measurement of red metal, fire, furnace and industrial environment.

In addition to the above common types of sensors, another commonly used form of sensor is the wire temperature sensor, especially the 2,3 and 4-wire series:

• 2-wire temperature sensor: Often used in situations where connection to short and low resistance wires is required, especially when testing an equivalent electrical circuit. With this type of sensor, the measured resistance will include both the part of the sensor (depending on temperature) and the resistance of the conductors used for the connection. The error of the sensor depends on the temperature and ambient factors.
• 3-wire temperature sensor: Provides a better level of measurement accuracy than the two-wire type, which is generally widely used in the industrial field. The three-wire technique eliminates errors caused by the resistance of the conductors; At the output, the voltage depends entirely on the resistance variation of the thermal sensor and is constantly adjustable according to temperature.
• 4-wire temperature sensor: Provides the maximum achievable accuracy, typically used only in laboratory survey applications. The measured voltage depends only on the resistance, and the accuracy of the measurement completely depends on the stability of the measured current and the error of the measuring device.

4. Application of temperature sensor

With high applicability and diversity, temperature sensors are commonly used in many different fields, including:

• Industry: Used in manufacturing processes and machine operations to ensure precise temperature control. For example, in the food and beverage industry, temperature sensors are used to monitor and control temperatures during processing and storage.
• HVAC (Heating, Ventilation, and Air Conditioning) systems: In HVAC systems, temperature sensors are used to measure and control temperatures in living and working spaces, helping to optimize energy efficiency and improve occupant comfort.
• Automotive: In the automotive industry, temperature sensors are used to monitor and control the temperature of engines, cooling systems, braking systems, and many other systems, helping to ensure vehicle performance and safety.
• Medical: In the medical field, temperature sensors are used in medical devices such as thermometers to measure a person’s body temperature. It can also be used in other medical devices such as devices that monitor the temperature of the medical sample storage medium.
• Heat treatment technology: In technological processes of heat treatment such as welding, forging, and firing, temperature sensors are used to ensure that the temperature is achieved working and controlled correctly.
• Research and development: In laboratories and research facilities, temperature sensors are used to collect temperature data in experiments and scientific studies, helping scientists and engineers better understand thermal processes and develop new technologies.

5. Precautions when using and storing

Temperature sensors play an integral role in maintaining a stable temperature for many industries. However, businesses need to carefully examine the following factors to ensure that the selection of sensor type is suitable for the measuring area, as they not only increase productivity and operational efficiency, but also create many other values in the manufacturing industry:

• Clearly define the purpose and environment in which the sensor is used.
• Make sure the insulation between the conductor and the sheath is large enough, especially at high temperatures.
• Check the installation depth of the sensor to avoid errors due to temperature differences.
• Avoid contact of sensor connectors with the measuring medium.

6. Summary

Above is the information about what is a temperature sensor? The structure and principle of operation of the temperature sensor? Hopefully, the above article will help your business better understand some necessary information of temperature sensors, thereby choosing the right type of sensor to apply to your production process.

In addition, if you are interested in other production solutions in the field of electronics and supporting industries,… Don’t forget to register for exciting exhibitions organized by RX Tradex in 2024 such as NEPCON Vietnam, Vietnam Manufacturing Expo, Metalex Vietnam, Waste & Recycling Vietnam Expo. This will be a great opportunity for your business to access the latest technologies from hundreds of famous machinery brands in the world, learn about optimal production solutions through listening to the sharing from leading experts. More specifically,  You can also promote your brand and products to many potential customers and partners, expand your business, improve the reputation and value of your brand in the market.