Physical constants play a central role in science and engineering, especially in the field of temperature measurement. Thermometers and thermocouples are crucial devices in measuring tools and are widely used in laboratories and industry. The accuracy of these tools has a direct impact on the reliability of the data, which in turn affects the accuracy of research and production. Ensuring the accuracy of these measurement tools is critical to maintaining high standards of experimental and engineering practice.
Determination of physical constants
overview
Physical constants are important parameters in the identification of compounds, including melting point, boiling point, density, refractive index, optical rotation, viscosity, and molecular weight. These constants help confirm the identity of a substance and its purity, and provide essential data in chemical research and industrial applications.
Temperature determination
Scale
The evolution of the international temperature scale was revised in 1954, 1968 and 1975. In 1954, the International Temperature Standard was introduced to improve measurement accuracy by defining new reference points. A more precise definition was introduced in 1968, with the main reference points including freezing and vapor points, and in 1975 it was further revised to improve the accuracy of the temperature range. These temperature scales provide a standard reference for all types of temperature measurements.
Mercury thermometer with calibration
Mercury thermometers are widely used due to their good linearity and high accuracy, but their disadvantages include a limited temperature range and the toxicity of mercury. Commonly used correction methods include liquid paraffin bath calibration, which is used to ensure the accuracy of the thermometer at the specified temperature point, and melting and boiling point corrections to compare the melting and boiling points of known substances. Red water glass thermometers are used as an alternative to mercury thermometers and are suitable for high or low temperature environments.
Beckman thermometer
Beckman thermometers have high accuracy and are used to measure temperature differences. Its structural design allows it to maintain high accuracy even under small temperature differences. When using, it is necessary to select the appropriate thermometer type, adjust the position of the mercury wire according to the measurement needs, and make a scale correction. When using, the influence of drastic temperature changes on the measurement results should be avoided, and the thermometer should be kept in a stable environment for measurement.
Thermocouple thermometer
Thermocouple thermometers work on the principle of thermoelectric potential, i.e. an electric potential is generated at the point of contact between two different metals due to a temperature difference. Common thermocouple types, such as type K, J, and T, each have different temperature ranges and accuracy. Thermocouples can be welded into thermopiles to improve measurement accuracy and stability, and are widely used in temperature measurement in industry and scientific research.
summary
Various temperature measuring instruments have their own advantages and disadvantages - mercury thermometers have good linearity but are toxic, suitable for medium and low temperature ranges; Beckman thermometers are highly accurate and suitable for small temperature difference measurements; Thermocouple thermometers are resistant to high temperatures and are widely used. The basic requirements for accurate temperature measurement include the selection of the right instrument, regular calibration, and the avoidance of interference with the measurement results by environmental factors. When using the instrument, it is necessary to pay attention to the operation specifications and maintenance of the instrument to ensure the accuracy and reliability of the measurement data.
