Temperature transducer refers to a sensor that can sense the temperature and convert it into an available output signal. Temperature sensor is the core part of temperature measuring instrument, which has a wide variety. According to the measurement method, it can be divided into contact type and non-contact type. According to the characteristics of sensor materials and electronic components, it can be divided into thermal resistance and thermocouple.

Main classification

Contact type

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

The thermometer achieves heat balance through conduction or convection, so that the indication value of the thermometer can directly represent the temperature of the measured object. Generally, the measurement accuracy is high. Within a certain temperature measurement range, the thermometer can also measure the temperature distribution inside the object. However, for moving bodies, small targets or objects with small heat capacity, there will be large measurement errors. The commonly used thermometers include bimetallic thermometers, glass liquid thermometers, pressure thermometers, resistance thermometers, thermistors and thermocouple. They are widely used in industry, agriculture, commerce and other sectors. In daily life, people often use these thermometers. With the wide application of low-temperature technology in national defense engineering, space technology, metallurgy, electronics, food, medicine, petrochemical and other departments and the research of superconducting technology, low-temperature thermometers for measuring temperatures below 120K have been developed, such as low-temperature gas thermometers, vapor pressure thermometers, acoustic thermometers, paramagnetic salt thermometers, quantum thermometers, low-temperature thermal resistors and low-temperature thermoelectric couples. Low temperature thermometer requires small volume, high accuracy, good reproducibility and stability of temperature sensing elements. The carburized glass thermal resistance made by carburizing and sintering porous high silica glass is a temperature sensing element of low-temperature thermometer, which can be used to measure the temperature in the range of 1.6 ~ 300K.

Non contact type

Its sensitive element and the measured object are not in contact with each other, 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 change (transient). It can also be used to measure the temperature distribution of temperature field.

The most commonly used non-contact temperature measuring instrument is called radiation temperature measuring instrument based on the basic law of blackbody radiation. Radiation thermometry includes brightness method (see optical pyrometer), radiation method (see radiation pyrometer) and colorimetric method (see Colorimetric Thermometer). Various radiation temperature measurement methods can only measure the corresponding photometric temperature, radiation temperature or colorimetric temperature. Only the measured temperature of blackbody (an object that absorbs all radiation and does not reflect light) is the real temperature. If the real temperature of the object is to be measured, the emissivity of the material surface must be corrected. The surface emissivity of materials depends not only on temperature and wavelength, but also on surface state, coating film and microstructure, so it is difficult to measure accurately. In automatic production, radiation thermometry is often used to measure or control the surface temperature of some objects, such as steel strip rolling temperature, roll temperature, forging temperature and the temperature of various molten metals in smelting furnace or crucible. In these specific cases, it is quite difficult to measure the emissivity of the object surface. For the automatic measurement and control of solid surface temperature, an additional mirror can be used to form a blackbody cavity with the measured surface. The effect of additional radiation can improve the effective radiation and effective emission coefficient of the measured surface. Using the effective emission coefficient, the measured temperature is corrected by the instrument, and finally the real temperature of the measured surface can be obtained. The most typical additional mirror is a hemispherical mirror. The diffuse radiation of the measured surface near the center of the ball can be reflected back to the surface by the hemispherical mirror to form additional radiation, so as to improve the effective emission coefficient ε Is the surface emissivity of the material, ρ Is the reflectivity of the mirror. As for the radiation measurement of the real temperature of gas and liquid medium, the method of inserting a heat-resistant material tube to a certain depth to form a blackbody cavity can be used. The effective emission coefficient of the cylindrical cavity after reaching thermal equilibrium with the medium is calculated. In automatic measurement and control, this value can be used to correct the measured cavity bottom temperature (i.e. medium temperature) to obtain the real temperature of the medium.

Advantages of non-contact temperature measurement: the upper limit of measurement is not limited by the temperature resistance of temperature sensing elements, so there is no limit on the maximum measurable temperature in principle. For high temperature above 1800 ℃, non-contact temperature measurement method is mainly adopted. With the development of infrared technology, radiation temperature measurement has gradually expanded from visible light to infrared. It has been adopted below 700 ℃ to normal temperature, and the resolution is very high.

Verification device

Verification regulation of temperature sensor:

1. Jjg229-2010 verification regulation of industrial platinum and copper thermistors

2. Verification regulation of jjg833-2007 standard group Platinum Rhodium 10 platinum thermocouple

3. Jjg141-2000 verification regulation of precious metal thermocouples for work

4. Jjg351-1996 verification regulation of low metal thermocouples for work

5. Jjg368-2000 verification regulation of copper copper nickel thermocouple for work

Verification standard and technical index of temperature sensor:

1. Measurement accuracy: grade 0.01; Resolution: 0.1uv and 0.1M Ω;

2. Parasitic potential of scanning switch: ≤ 0.4 μ V;

3. Temperature range: water tank: (room temperature + 5 ~ 95) ℃ oil tank: (95 ~ 300) ℃ low temperature constant temperature tank: (- 80 ~ 100) ℃ high temperature furnace: (300 ~ 1200) ℃;

4. Temperature control stability: better than 0.01 ℃ / 10min (oil tank, water tank, low temperature constant temperature tank); 0.2 ℃ / min (tubular verification furnace);

5. Total uncertainty: for thermocouple verification, the measurement uncertainty is better than 0.7 ℃, and the repeatability error is less than 0.25 ℃; The measurement uncertainty of thermal resistance verification is better than 50mk, and the repeatability error is less than 10mk;

6. Verification quantity: check (1-8) thermocouples and (1-7) heating resistors in the same line at the same time;

7. Working power supply: AC220V ± 10%, 50Hz, with good protective grounding;

8. High temperature furnace power: About 2kW;

9. Thermostatic bath power: About 2kW;

10. Power of microcomputer measurement and control system: < 500.

Functions and features of temperature sensor verification device:

1. Verify K, e, J, N, B, s, R, t and other types of working thermocouples;

2. Verify PT100, pt10, cu50, cu100 and other working thermal resistance, glass liquid thermometer, pressure thermometer and bimetal thermometer;

3. Multi channel low potential automatic transfer switch, parasitic potential ≤ 0.4 μ V;

4. Control 1-4 high temperature furnaces;

5. Temperature field test: it can test the temperature field of verification furnace, oil tank, water tank and low-temperature constant temperature tank;

6. Wire system conversion: two wire system, three wire system and four wire system resistance verification can be carried out;

7. The software has the functions of comparison experiment, repeatability experiment, temperature field experiment and other related experiments;

8. On the platform above Windows2000 / XP, all Chinese interface and standard Windows operating system are convenient and fast. Achievable:

1) Equipment self inspection and line inspection;

2) Display and save the temperature control curve on the screen ≤ 0.4 μ V;

3) Automatic collection of test data;

4) Automatically generate verification records that meet the requirements;

5) The verification results are saved automatically and cannot be changed manually;

6) Query all kinds of thermocouples, thermal resistance index tables and other help;

7) Intelligent management function of all historical verification data, temperature control curve query statistics and measurement of thermocouple and thermal resistance.