High temperature and humidity sensorThe basic form is to measure humidity by utilizing the adsorption capacity of moisture sensitive materials for water molecules or by producing physical effects on water molecules. There have been records of humidity measurement as early as the 16th century. Many ancient measurement methods, such as dry wet bulb thermometers, hair hygrometers, and dew point meters, are still widely used today. Modern industrial technology requires high-precision, high reliability, and continuous measurement of humidity, resulting in the emergence of a wide variety of humidity sensitive components.
High temperature and humidity sensorMeasurement method:
Common humidity measurement methods include: dynamic method (dual pressure method, dual temperature method, split current method), static method (saturated salt method, sulfuric acid method), dew point method, dry wet bulb method, and electronic sensor method.
① The dual pressure method and dual temperature method are based on the thermodynamic principles of p, v, and t equilibrium, with longer equilibrium times. The split flow method is based on the mixing of moisture and dry air. Due to the use of modern measurement and control methods, these devices can be made quite precise. However, due to their complexity, high cost, and time-consuming operation, they are mainly used as standard measuring devices, with measurement accuracy of over ± 2% RH.
② The saturated salt method in static measurement is the most common and simple method for humidity measurement. However, the saturated salt method requires strict equilibrium between liquid and gas phases, and has high requirements for stable environmental temperature. It takes a long time to balance when used, and even longer for low humidity points. Especially when there is a large difference between indoor humidity and the humidity inside the bottle, it takes 6-8 hours to balance each time it is opened.
③ The dew point method is a direct result of thermodynamics that measures the temperature at which humid air reaches saturation, with high accuracy and a wide measurement range. The precision dew point meter used for measurement can achieve an accuracy of ± 0.2 ℃ or even higher. However, cold mirror dew point meters based on modern photoelectric principles are expensive and often used in conjunction with standard humidity generators.
④ The dry wet bulb method is a moisture measurement method invented in the 18th century. With a long history, it is widely used. The dry wet bulb method is an indirect method that converts humidity values using the dry wet bulb equation, which is conditional: the wind speed near the wet bulb must be above 2.5m/s. The commonly used dry wet bulb thermometer simplifies this condition, so its accuracy is only 5-7% RH, and the dry wet bulb does not belong to the static method. Do not simply think that improving the measurement accuracy of two thermometers is equivalent to improving the measurement accuracy of the hygrometer.
⑤ Electronic humidity sensor method
Electronic humidity sensor products and humidity measurement belong to the industry that emerged in the 1990s. In recent years, significant progress has been made in the research and development of humidity sensors both domestically and internationally. Humidity sensors are rapidly developing 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.