There are many kinds of temperature measuring instruments, such as gas thermometers, thermocouple thermometers, low temperature thermometers, etc. Many users have a variety of temperature measuring instruments and what are the uses? Do you know tomorrow? For the family, please introduce the classification and use of temperature measuring instruments in detail.
1. Gas thermometer: use hydrogen or helium as the temperature measurement material. Because the liquefaction temperature of hydrogen and helium is very low, it is close to zero, so its temperature measurement range is very wide. This thermometer is highly accurate and is used for fine measurement.
2, resistance thermometer: divided into metal resistance thermometer and semiconductor resistance thermometer, are based on the characteristics of the resistance value changes with temperature. Metal thermometers are important for pure metals such as platinum, gold, copper, and nickel, and bismuth iron and phosphor bronze alloys; carbon thermometers are important for semiconductor thermometers. Resistance thermometers are easy to use and are widely used. Its measurement range is -260 ° C to 600 ° C.
3. Thermocouple Thermometer: It is a kind of temperature measuring instrument commonly used in industry. It is made of a thermoelectric image. Two different kinds of wire welding are combined to form the task end, and the other two are connected with the measuring instrument to form a circuit. When the task end is placed at the temperature to be measured and the temperature between the task end and the free end is different, an electromotive force is present, so that a current flows through the circuit. Through the measurement of the electrical quantity, the temperature at the other place can be measured by applying the temperature at the known place. This kind of thermometer is mostly made of copper--constantan, iron--constantan, nickel--constantan, gold-cobalt--copper, platinum--anthracene. It is used between the two materials with different temperature difference, and is mostly used for low temperature and low turbidity measurement. Some thermocouples can measure temperatures as low as 3000 °C, and some can measure high temperatures at relatively zero degrees.
4, low temperature thermometer: refers to the thermometer used to measure the temperature above 500 ° C, there are light thermometer, colorimetric thermometer and radiation thermometer. The principle and structure of the low temperature thermometer are quite complicated and will not be discussed here. The measurement range is from 500 °C to 3000 °C, which is not used to measure high temperature.
5, pointer thermometer: is a thermometer like a dashboard, also known as the thermometer, used to measure room temperature, is made of metal thermal expansion and contraction. It uses a bimetal as a temperature sensing element to hold the pointer. The bimetal is usually riveted with copper and iron, and the copper is on the left and the iron is on the right. Because the thermal expansion and contraction of copper is more than that of iron, when the temperature is lowered, the copper piece pulls the iron piece to the right, and the pointer is deflected to the right under the mobilization of the bimetal (pointing to low temperature); As the temperature goes low, the pointer deflects to the left (pointing to high temperature) under the mobilization of the bimetal.
6, glass tube thermometer: glass tube thermometer is the application of thermal expansion and contraction to achieve temperature measurement. Because of the difference between the shrinkage coefficient of the temperature measuring medium and the boiling point and the condensation point, it is important that the glass tube thermometers that are rare are: a fire thermometer, a mercury thermometer, and a red pen water thermometer. His strengths are simple structure, convenient application, high measurement accuracy and high price. The problem is to measure the high and low limits and the accuracy of the glass quality and temperature measurement medium. And can not be far from the distance, fragile.
7. Pressure type thermometer: The pressure type thermometer is used to seal the liquid in the container. When the gas or the saturated gas is heated, the volume shrinkage or pressure change occurs as a test signal. Its basic structure consists of a warm pack, a capillary and a helium to make the three parts of the table. It is one of the first methods used to control the temperature of the production process. The pressure-type temperature measurement system was still on the spot and used a very common measurement method in the control temperature. The strengths of the pressure thermometer are: simple structure, high machine strength, not afraid of shock. It is expensive and does not require external power. The problem is: the temperature range is unlimited, and the temperature is -80~400 °C; the heat loss is slower; the instrument sealing system (warm pack, capillary tube, spring tube) is difficult to repair and must be replaced; the measurement accuracy depends on the temperature The influence of the temperature of the warm pack device is relatively large, and the precision is absolutely low; the capillary transfer interval is not limited. The scope of the task of the pressure thermometer should be in the range of 1/2--3/4 of the measurement category, and the performance table and the temperature package should be placed as close as possible. The bolts of the warm pack device used in the device will cause the temperature to be lost and the temperature will be forbidden. When the device is installed, the heat preservation treatment should be stopped, and the warm pack task should not be shocked.
8. Dynamic thermometer: The dynamic thermometer is made of a curled bimetal. The bimetal has one end that is strong and the other end that carries the pointer. Due to the difference in shrinkage level between the two metal sheets, the difference in the curl level of the bimetal is formed at different temperatures, and the pointer is then referred to the difference position on the dial. The reading from the dial can be used to know the temperature.
9. Semiconductor thermometer: The resistance change of the semiconductor is different from that of the metal. When the temperature is lowered, the resistance increases, and the change range is larger. Therefore, a large number of temperature changes can also make a significant change in the resistance, and the resulting thermometer has a high degree of fineness, often referred to as a temperature sensor. Stainless steel electrode
10. Thermocouple Thermometer: The thermocouple thermometer consists of two differential metal and a sharp voltmeter. Metal junctions at different temperatures will cause differential potential differences at the ends of the metal. The potential difference is very small, so a sharp voltmeter is needed to measure it. From the reading of the voltmeter, you can know the temperature.
11. Photometric low temperature meter: If the temperature of the object is high enough to recover the visible light, the temperature of the heat radiation can be measured to determine the temperature. The thermometer is a light measuring thermometer. This thermometer is importantly made up of a celite mirror with a white filter and a set of circuits with small lamps, galvanometers and variable resistors. Before application, the relationship between the temperature corresponding to the difference in brightness of the filament and the reading on the ammeter is established. When applied, the mirror is aligned with the object to be tested, and the resistance is adjusted so that the brightness of the lamp is the same as that of the object to be tested. At this time, the temperature of the object to be tested can be read from the ammeter.
12, liquid crystal thermometer: liquid crystal made with differential formula, its phase change temperature difference, when its phase change, its optical properties will also change, so that the liquid crystal looks colored. If the liquid crystal with a different phase change temperature is applied to a piece of paper, the temperature can be known by changing the color of the liquid crystal. The advantage of this thermometer is that the reading is easy, and the fault is the lack of accuracy, which is often used in indecent fish tanks to make the water temperature.
The classification and use of the temperature measuring instrument was once completed. At the beginning, the family knew what the temperature measuring instrument had and its classification and use. In the current application process, it knows its common sense, and the application will become more and more applicable. Easy.
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