How is temperature measured and how is it measured with a temperature measuring instrument?

Experiment 04 Measuring Temperature with a Common Thermometer.

Most of the glass thermometers we usually use are mercury thermometers, which contain mercury. The boiling point of mercury is sufficient, which is sufficient for measuring the general air temperature. However, in industry, temperatures of thousands of degrees are sometimes measured, so mercury thermometers are not available.

Gallium metal was turned to help.

Gallium has a high boiling point of 2070 but a low melting point only. In other words, if you put gallium in your hand, you can melt it at human temperature. This property dictates that gallium is the most suitable for measuring temperatures in 2070.

People fill gallium into high-temperature quartz tubes to make high-temperature temperature main, which is widely used in industrial fields.

Thermocouple thermometers are used for ultra-high temperature measurements, and it works on the following principles:

When two different conductors come into contact to form a loop, an electric potential is generated in the loop, and the magnitude of this electric potential is directly related to the temperature difference between the two contacts, a phenomenon called the thermoelectric effect. The thermocouple is a thermocouple made of a thermoelectric element, and a thermocouple thermometer is a thermocouple thermometer.

In classical electronic theory, the thermoelectric potential is composed of two parts: the temperature difference potential and the contact potential.

The temperature difference potential is caused by the temperature difference between the two ends of a homogeneous conductor. The contact potential is formed when two different conductors A and B come into contact and are formed by the diffusion of electrons at the contact point due to the different free electron densities of the two conductors. The contact potential is not only a function of temperature t, but also contributes much more to the thermoelectric potential than the temperature difference potential.

The thermoelectric potential generated by the thermocouple due to temperature change is measured, and the temperature value that causes the thermoelectric potential can be known based on the functional relationship between the thermoelectric potential and the temperature change.

Based on the idea proposed by the British astronomer Samson in 1894 that the way the sun transmits energy is mainly radiation, rather than convection, Eddington established a model of the sun based on the thermal equilibrium of ideal gases, and he assumed that the sun's elemental proportions are similar to those of the earth, and they are all in a state of hot gas. In 1926, he succeeded in calculating that the central temperature of the sun was 39 million degrees. Later, after learning from the work of astronomer Payne that hydrogen is the main component of the Sun or other stars, Eddington reconsidered his model and corrected the temperature of the Sun's center to 19 million degrees.

In 1938, Bethe of the United States and von Weizsacher of Germany calculated the process of fusion of protons (i.e., protons) into helium nuclei, respectively, and obtained that the temperature of the fusion of the nuclear fusion in the center of the sun was more than 18 million degrees, which was consistent with the results calculated by Eddington purely by the theory of gas heat equilibrium. The mystery of solar energy generation has finally been satisfactorily solved.

I know that the current temperature measurement can be accurate to the degree, and it is technically possible to be more precise, but it is not very practical to be overly accurate.

The zero degree that is defined as the thermodynamic temperature scale (absolute temperature scale) is called absolute zero.

In 1592, Galileo created the first thermometer. It was a straight, slender glass tube with a scale, which was marked at an equidistant distance on the tube. The closed end is spherical, and the other end is pre-filled with some colored water in the tube and the unclosed end is inserted upside down into the container containing the water.

When the ambient air temperature changes, the height of the water column in the pipe also changes. When the outside temperature rises, the gas in the glass ball expands, which lowers the water level in the glass tube; Conversely, when the temperature is lower, the gas in the glass ball shrinks, and the water level in the glass tube rises. This tells you how high and low the temperature is.

1. The earliest thermometer was invented in 1593 by the Italian scientist Galileo Galilei (1564 1642). His first thermometer was a glass tube with an open end and a walnut-sized glass bubble at the other. To use, heat the glass bubble and insert the glass tube into the water.

As the temperature changes, the water surface in the glass tube moves up and down, and the temperature change and temperature can be determined according to the amount of movement. The thermometer has the effect of thermal expansion and contraction, so this kind of thermometer is greatly affected by environmental factors such as external atmospheric pressure, so the measurement error is large.

Qiaoqiao's method of measuring temperature:

Balanced expansion temperature measurement method: It mainly uses the principle of thermal expansion and cold contraction of the substance, that is, the temperature measurement is carried out according to the relationship between the volume or geometric deformation of the object and the temperature; Electric temperature measurement method: mainly use the single value relationship between the potential, resistance or other electrical properties of the material and the temperature for temperature measurement, including thermocouple temperature measurement, thermal resistance temperature measurement, integrated chip temperature measurement, etc.; Integrated chip temperature measurement:

The intelligent temperature sensor adopts digital technology, adopts a single-wire interface mode, supports multi-point networking function, does not need any wide finger peripheral components in use, and the temperature measurement range is minus 55 to 125.

Temperature measurement is a quantitative measurement of the temperature of an object with a thermometer.

The measurement of a thermophysical quantity is actually a certain quantity of the object, and the physical quantity should make a monotonous and significant change with the change of the temperature of the object within a certain temperature range. According to the laws of physics, the temperature of the measured object is displayed by the numerical value of the physical quantity.

Bimetal thermometer:

When the temperature changes, due to the different elongation of the two metals, the other end is displaced, driving the pointer to deflect to indicate the temperature. A bimetal thermometer for industrial use consists of a thermometer rod (including a temperature sensor and a protective tube) and a dial (including hands, dial and glass shield). The temperature range is -80 600 °C.

It is suitable for temperature measurement where industrial precision is not required.

A constant pressure gas thermometer keeps its pressure unchanged for a certain mass of gas, and uses volume as a symbol of temperature. It is only used to measure thermodynamic temperature (see thermodynamic temperature scale) and is rarely used for actual temperature measurements.

Pressure thermometry uses pressure as a marker of temperature. There are three types of thermometers in this category: industrial pressure gauge thermometers, constant volume gas thermometers, and vapor pressure thermometers at low temperatures.

Temperature measurement methods: There are two main categories:

Contact Temperature Measurement Method:

1. Expansion temperature measurement method: Expansion temperature measurement is a traditional temperature measurement method, which mainly uses the principle of thermal expansion and cold contraction of substances.

2. Electric temperature measurement method: The electric temperature measurement method mainly uses the single value relationship between the potential, resistance or other electrical properties of the material and the temperature for temperature measurement.

3. Contact photoelectric and thermal color temperature measurement method: The contact photoelectric temperature measurement method mainly refers to the method of measuring the temperature by contacting the measured object, drawing out the thermal radiation or other optical signals caused by temperature changes, and detecting the changes through photoelectric conversion devices. The thermochromatic temperature measurement method mainly indicates the temperature by indicating the change of the color of the sensitive material at different temperatures.

Non-contact measurement methods:

1. Radiative temperature measurement method: The radiation temperature measurement method is based on the law of thermal radiation.

2. Spectral method temperature measurement method: The contact spectral temperature measurement method is mainly suitable for the measurement of high temperature flame and gas flow temperature. The principle is as follows: it mainly measures the temperature by detecting the wax state excitation spectral signal of the measured medium.

3. Laser interferometry temperature measurement method: laser speckle photography, schlieren method and interferometry method are all based on the principle of light interference, which is suitable for the measurement of high temperature flame and air flow temperature.

Temperature measurement is a quantitative measurement of the temperature of an object with a thermometer.

The measurement of the physical quantity of temperature is actually a certain quantity of the object, and the physical quantity should make a monotonous and significant change with the change of the temperature of the object within a certain temperature range. According to the laws of physics, the temperature of the measured object is displayed by the numerical value of the physical quantity.

Introduction

The temperature of the object is quantitatively measured by the thermometer, and when measuring the temperature, a physical quantity that changes with the temperature within a certain temperature range is always selected as the temperature marker, and the temperature of the measured object is displayed by the numerical value of the physical quantity according to the physical law on which it is based.

At present, there are dozens of methods for measuring temperature. According to the physical laws on which temperature measurement is based and the physical quantities selected as temperature markers, measurement methods can be summarized into the following categories.

The glass bubble of the thermometer is fully immersed in the liquid to be measured, and does not touch the bottom or wall of the container; After the thermometer glass bubble is immersed in the measured liquid, wait for a while, and then read it after the thermometer indicator is stable; The glass bubble of the thermometer should remain in the liquid during reading, and the line of sight should be level with the upper surface of the liquid pillar in the thermometer.

When measuring the surface temperature of a luminous object, such as aluminum and stainless steel, the reflection of the surface can affect the infrared thermometer reading. Before reading the temperature, a strip can be placed on the metal surface, and after the temperature is balanced, the temperature of the strip area is measured.

In order for an infrared thermometer to provide accurate temperature measurement from the kitchen to the refrigerated area, it is necessary to wait for a period of time in the new environment to reach temperature equilibrium. It is best to place the thermometer in a place where it is used frequently.

An infrared thermometer is used to read the internal temperature of a fluid food, like a soup or sauce, which must be stirred and then the surface temperature can be measured. Keep the thermometer away from steam to avoid contaminating the lens, resulting in incorrect readings.