Temperature and hygrometer measurement methods - Database & Sql Blog Articles

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What are the measurement methods of the hygrometer?

Humidity and humidity meter definition: In the measurement method, humidity is defined as the "amount of object state". The steam flow meter says: The humidity referred to in daily life is relative humidity, expressed as RH%. In summary, the percentage of the amount of water vapor (water vapor pressure) in a gas (usually in air) and the amount of saturated water vapor (saturated water vapor pressure) in the same condition as air. Humidity has a close relationship with life long ago, but it is more difficult to express it by quantity. The means of expressing humidity are absolute humidity, relative humidity, dew point, moisture to dry gas ratio (weight or volume), and the like.

Hygrometer classification: according to the measurement method classification 1. dry and wet bulb hygrometer; 2. dew point hygrometer; 3. hair hygrometer 4. coulometer hygrometer; 5. electrochemical hygrometer; 6. optical hygrometer

What are the measurement methods of the hygrometer?

Humidity measurement method: The humidity measurement of the temperature and humidity meter is divided into two or thirty kinds in principle. But humidity measurement has always been one of the famous problems in the world of metrology. A seemingly simple measure of value, involving quite complex physics-chemical theoretical analysis and calculations, may involve many factors that must be noted in humidity measurement, thus affecting the rational use of the sensor. Steam flowmeter says: Common humidity measurement methods are: dynamic method (double pressure method, double temperature method, split method), static method (saturated salt method, sulfuric acid method), dew point method, dry and wet ball method and electronic sensor method . 1 Double pressure method and double temperature method are based on the thermodynamic P, V, T balance principle, and the equilibrium time is long. The split method is based on the precise mixing of absolute moisture and absolute dry air. Due to the use of modern measurement and control methods, these devices can be made quite sophisticated, but because of the complexity and cost of the equipment, the operation is time-consuming and labor-intensive, mainly used as a standard measurement, the measurement accuracy can reach ± ​​2% RH or more. 2 The saturated salt method in the static method is the most common method in humidity measurement and is simple and easy. However, the saturated salt method requires strict balance between liquid and gas phases, and requires high stability to ambient temperature. It is required to wait for a long time to balance, and the low humidity point requires longer. Especially when the indoor humidity and the humidity inside the bottle are large, it needs to be balanced for 6~8 hours each time. 3 The dew point method is to measure the temperature when the humid air reaches saturation. It is a direct result of thermodynamics, with high accuracy and wide measuring range. The accuracy of the precision dew point meter for measurement can reach ±0.2 °C or even higher. However, the cold mirror dew point meter using the modern light-electric principle is expensive and often used in conjunction with a standard humidity generator. 4 Dry and wet ball method, this is the method of measuring humidity invented in the 18th century. It has a long history and is most commonly used. The dry-wet ball method is an indirect method that converts the humidity value using the dry-wet ball equation, which is conditional: the wind speed near the wet ball must be above 2.5 m/s. Ordinary dry and wet bulb thermometers simplify this condition, so its accuracy is only 5~7% RH. Dry and wet bulbs are not static. Do not simply think that increasing the measurement accuracy of two thermometers is equivalent to increasing the humidity. The measurement accuracy of the meter. 5 Electronic humidity sensor method Electronic humidity sensor products and humidity measurement belong to the industry that emerged in the 1990s. In recent years, domestic and foreign companies have made great progress in the research and development of humidity sensors. Humidity sensors are rapidly evolving from simple humidity sensors to integrated, intelligent and multi-parameter detection, creating favorable conditions for the development of a new generation of humidity measurement and control systems, and raising humidity measurement technology to a new level.

What are the measurement methods of the hygrometer?

Thermo-hygrometers have been widely used in industry, agriculture, meteorology, medical care, and daily life. Especially with the development of science and technology, the detection and control of humidity has received more and more attention and a lot of research and development. jobs. Generally, the characteristic requirements of an ideal humidity sensor are that it is suitable for use in a wide temperature range and a wet range, and has high measurement accuracy; long service life and good stability; fast response speed, small hysteresis hysteresis, and reproducibility. Good; high sensitivity, good linear shape, small temperature coefficient; simple manufacturing process, easy mass production, simple conversion circuit, low cost; corrosion resistance, low temperature resistance and high temperature characteristics.