Banner Sensors - Introduction to the main classifications and uses of temperature sensors

A temperature sensor is a sensor that senses the temperature and converts it into a usable output signal. Temperature sensors are the heart of temperature measuring instruments and come in a wide variety of varieties. According to the measurement method, it can be divided into two categories: contact and non-contact, and according to the characteristics of sensor materials and electronic components, it can be divided into two categories: thermal resistance and thermocouple.

Temperature sensors are mainly classified

According to the measurement method, it can be divided into two categories: contact temperature sensor and non-contact temperature sensor, and according to the characteristics of sensor materials and electronic components, it can be divided into two categories: thermal resistance temperature sensor and thermocouple temperature sensor.

1. Contact type: The detection part of the contact temperature sensor has good contact with the measured object, also known as the thermometer.

The thermometer achieves thermal equilibrium by conduction or convection, so that the thermometer's indication directly represents the temperature of the object being measured. In general, the measurement accuracy is high. Within a certain temperature range, a thermometer can also measure the temperature distribution inside an object. However, for moving bodies, small targets or objects with small heat capacity, large measurement errors will be generated, and commonly used thermometers include bimetal thermometers, glass liquid thermometers, pressure thermometers, resistance thermometers, thermistors and thermocouples.

2. Non-contact: its sensitive components are not in contact with the measured object, also known as non-contact temperature measuring instrument. This instrument can be used to measure the surface temperature of moving objects, small targets, and objects with small heat capacity or rapid temperature changes (transients), as well as to measure the temperature distribution of the temperature field.

The most commonly used non-contact temperature measuring instruments are based on the basic law of blackbody radiation, known as radiometric thermometers. Radiometric thermometry includes luminance (see Optical pyrometers), radiometry (see Radiation pyrometers), and colorimetric methods (see Colorimetric thermometers). Various radiometric temperature measurement methods can only measure the corresponding photometric temperature, radiation temperature or colorimetric temperature. Only the temperature measured on a black body (an object that absorbs all radiation but does not reflect light) is the true temperature.

Advantages of non-contact temperature measurement: The upper limit of measurement is not limited by the temperature resistance of the temperature sensing element, so there is no limit to the maximum measurable temperature in principle. For high temperatures above 1800°C, non-contact temperature measurement methods are mainly used. With the development of infrared technology, radiation temperature measurement has gradually expanded from visible light to infrared, and has been used below 700 °C until room temperature, and the resolution is very high.

The main purpose of temperature sensors

Temperature is a physical quantity that characterizes the degree of cold and heat of an object, and is a very important and common measurement parameter in the process of industrial and agricultural production. Temperature measurement and control play a very important role in ensuring product quality, improving production efficiency, saving energy, production safety, and promoting the development of the national economy. Due to the ubiquity of temperature measurement, the number of temperature sensors ranks first among all kinds of sensors, accounting for about 50%.

Temperature sensors measure indirectly by changing certain properties of an object as it changes with temperature. The characteristics of many materials and components change with the change of temperature, so there are quite a lot of materials that can be used as temperature sensors. The physical parameters of the temperature sensor change with temperature include: expansion, resistance, capacitance, and electromotive force, magnetic properties, frequency, optical properties, and thermal noise. As production evolves, new types of temperature sensors will emerge.

Due to the extremely wide range of temperature measurement in industrial and agricultural production, from minus hundreds of degrees to minus thousands of degrees, temperature sensors made of various materials can only be used in a certain temperature range.

There are two main types of contact between temperature sensors and the medium being measured: contact and non-contact. Contact temperature sensors need to be in thermal contact with the medium being measured, so that the two can exchange sufficient heat to reach the same temperature. This type of sensor mainly includes resistive type, thermocouple, PN junction temperature sensor, etc. The non-contact temperature sensor does not need to be in contact with the measured medium, but is transmitted to the temperature sensor through the thermal radiation or convection of the measured medium to achieve the purpose of temperature measurement. This type of sensor mainly includes infrared temperature sensors. The main feature of this temperature measurement method is that it can measure the temperature of a moving substance (e.g., the bearing temperature of a slow-moving train, the temperature of a rotating cement kiln) and the temperature of an object with a small heat capacity (e.g., the temperature distribution in an integrated circuit).

Banner Sensors - Introduction to the main classifications and uses of temperature sensors

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