Characteristics and development trend of the hotte

2022-07-24
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Characteristics and development trend of temperature measurement technology

temperature sensor refers to a sensor that can sense temperature and convert it into usable output signal. Temperature is a physical quantity closely related to human living environment. It is one of the three parameters (flow, pressure and temperature) of industrial process and one of the seven basic physical quantities in the international system of units (SI). Temperature measurement is a classic and ancient topic. For a long time, a variety of temperature measuring elements and sensors have been popularized in this field. However, until today, in order to meet the extensive requirements of various industrial departments, scientific research, medical treatment, household appliances and other aspects, new temperature measuring elements and sensors, new temperature measuring methods, new temperature measuring materials and new market applications are still being developed. It is not easy to measure the temperature accurately. For example, if the temperature measuring element is improperly selected and the measurement method is inappropriate, the satisfactory results can not be obtained

according to the statistics of the leather pulling mechanism, the sales of sensors in China in 2009 was 32.7 billion yuan, of which temperature sensors accounted for 14% of the total sensor market, mainly used in the fields of communication electronics, household appliances, building automation, medical equipment, instrumentation, automotive electronics, etc

bimetallic thermometer TBI with sanitary clamp type process connection, for temperature measurement in sanitary applications

(picture source: baomeng company)

characteristics of temperature sensor

as an ideal temperature sensor, it should have the following requirements: wide measurement range, high precision, good reliability, small time drift, light weight, fast response, low price, mass production, etc. However, temperature sensors that meet the above conditions do not exist, and various temperature sensors should be used flexibly according to the application site. This is because different temperature sensors have different characteristics

● different temperature sensors have different measuring ranges and characteristics

the temperature measurement range and characteristics of several important types of temperature sensors are shown in Table 1. Table 1. Classification of temperature measurement sensor and temperature measurement range

● the accuracy of temperature measurement is related to the measurement method

according to the use method of temperature sensor, it is usually divided into contact measurement and non-contact measurement. The characteristics of the two measurement methods are shown in Table 2. Table 2. Comparison between contact measurement and non-contact measurement

● different temperature measuring elements shall adopt different measuring circuits

there are three types of measuring circuits commonly used. "Measuring circuit of resistance temperature measuring element", the transparent plastic lunch box with clean measuring circuit is sometimes considered to eliminate the influence of nonlinear error and thermal resistance wire on measurement accuracy. "Potential type temperature measuring element measuring circuit", which needs to consider linearization and cold end compensation, and the signal processing circuit is more complex than the thermal resistance. "Current type temperature measuring element measuring circuit", the semiconductor integrated temperature sensor is the most typical current type temperature measuring element. When the power supply voltage changes and the external wire changes, the output current of the circuit is basically unaffected, which is very suitable for long-distance temperature measurement

Latest progress in temperature measurement

● develop temperature measuring elements and temperature sensors suitable for various industrial applications

platinum film temperature sensor film thickness 1 μ m. It can be placed in a very small measuring space to measure the distribution of temperature field. The response time is not more than 1ms. The minimum diameter of even wire is 25 μ m. Thermocouple volume less than 1 × Mm3, mass less than 1 μ g。

the multi-color colorimetric temperature sensor can calculate the approximate emissivity of the measured object in real time and improve the accuracy of radiation temperature measurement

the temperature resolution of the resonant quartz tuning fork temperature sensor can reach 0.0009 ℃, the accuracy can reach 0.02 ℃, the measurement range can reach -200 ~ 260 ℃, and the linearity can reach 0.1 ~ 0.05%

The new temperature control device composed of

z- elements has the characteristics of simple circuit structure, high precision, fast speed, low power consumption and low cost

the integrated temperature sensor is made of diffused silicon technology, which is suitable for mass production with good consistency and sensitivity of 11.3/℃

w-re temperature sensor the high temperature sensor made of W-Re thermocouple can detect the upper limit temperature of 2300 ℃, which is suitable for high temperature measurement in reducing, inert, vacuum, nuclear radiation and other environments

intelligent temperature sensor uses MEMS technology to combine typical temperature measuring elements, signal conditioning circuits and microprocessors with digital bus interface to form an intelligent temperature sensor system

● temperature measurement technology has developed from "wired" to "wireless"

the traditional temperature measurement usually adopts the wired connection method with cables. However, for some occasions, such as temperature measurement of rotating or moving objects, places where people can't get in the harsh environment, and wired environment is not suitable, with the application of intelligent temperature sensors and in consideration of saving wiring costs, the temperature measurement technology begins to develop from "wired" to "wireless"

the wireless temperature measurement virtual instrument system using passive SAW resonator introduces signal processing method and feedback control, which reduces the system cost and improves the measurement accuracy and distance. Combined with the general computer platform and data i/o board, it can be flexibly controlled by software, and can automatically adjust the measurement parameters according to different environments and measurement processes to achieve adaptive detection. When the transmitting power is 100MW and the wireless detection distance is 4m, the uncertainty of repeated measurement of resonance frequency is about 0.09khz, and the uncertainty of temperature measurement sensitivity at 3M is about 0.1 ℃

temperature and humidity sensor system for air conditioning the system has two parts: host and extension. The extension regularly transmits the data measured by the internal temperature and humidity sensors to the host in a wireless manner. The host converts it into an electrical signal through the output unit and sends it to the control device. As the extension is powered by battery, it can be placed anywhere and the control signal can be transmitted wirelessly, which is very convenient

for the data measured by the sensors installed on the site, the wireless patrol inspection system does not need inspectors to go to the site for visual inspection or recording, but carries out wireless patrol inspection on the field sensors with wireless transmission mode through the wireless data collection system. This detection system will be very convenient for the detection of dangerous places and high parts

● temperature measurement technology develops in the direction of "from point to line, from line to surface, and from surface to interior"

the traditional temperature measurement of multi-core thermocouples is mainly based on "point" temperature measurement. However, people often need to pay attention to the temperature distribution of the whole temperature field, such as the temperature distribution of the whole furnace, the temperature field in the diffusion furnace, and the temperature of each point in the warehouse. Therefore, multi-core armored thermocouples have emerged, or multiple thermocouples are assembled along the cable with temperature measuring cables, or the "linear" temperature distribution is measured by thermal resistance

optical fiber temperature distribution measurement technology optical fiber temperature distribution measurement technology is an epoch-making technology that can measure linear temperature distribution with one sensor. The basic principle of this technology is to shoot the laser pulse into the optical fiber, and calculate its temperature according to the ratio of Stoke and anti stoke light in the scattered light returned everywhere. This optical fiber temperature distribution measurement technology can measure the temperature distribution within 30km of learning from foreign advanced experience. It is ideal to measure the temperature distribution of oil well from surface to underground depth

measuring surface temperature distribution with radiation thermometer or thermal imager for the measurement and control of object surface temperature, radiation thermometer and thermal imager were used in the past, such as measuring the temperature distribution of blast furnace outer surface layer in iron and steel plant with thermal imager, measuring the surface temperature monitoring of rotary furnace in cement industry with infrared radiation thermometer, etc. However, if the optical fiber temperature distribution measurement technology is used, it can not only improve the measurement accuracy, but also greatly reduce the cost

the method of lengthening thermocouple can be used for deep temperature measurement, but it is very inconvenient to use. Special device for deep temperature measurement can be adopted, which is composed of heater, metal frame, insulation layer and temperature measuring element (such as thermistor). The principle is that the temperature gradient can be eliminated on the surface of the heater, and the surface temperature can be measured by strain control, so as to know the deep temperature. (end)

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