there are 2-3 kinds of humidity measurement in principle, but humidity measurement is always one of the difficult problems in the world measurement field. A seemingly simple value, in deep study, involves quite complicated physical-chemical theoretical analysis and calculation, and beginners may ignore many factors that must be paid attention to in humidity measurement, thus affecting the rational use of sensors.
The common methods of humidity measurement are: dynamic method (double pressure method, double temperature method and shunt method), static method (saturated salt method and sulfuric acid method), dew point method, dry and wet bulb method and electronic sensor method. However, for the requirement of accurate sensing and real-time control in HVAC control, electronic humidity sensor method is a development trend. Electronic humidity sensor products and humidity measurement belong to the industries that rose in the 199s. In recent years, great progress has been made in the research and development of humidity sensors at home and abroad. Humidity sensor is developing rapidly from simple humidity sensor to integrated, intelligent and multi-parameter detection, which creates favorable conditions for developing a new generation of humidity measurement and control system and raises humidity measurement technology to a new level.
the first lithium chloride electro-humidity sensor based on the principle of resistance-humidity characteristics was developed by F.W.Dunmore of American Bureau of Standards. This kind of element has a series of advantages, such as high precision, simple structure and low price, and is suitable for measurement and control at room temperature and humidity. The measuring range of lithium chloride element is related to the concentration of lithium chloride and other components in the humidity sensitive layer. The effective humidity sensing range of a single element is generally within 2%RH. For example, the humidity sensitive range of .5% concentration is about (8~1)%RH, and the corresponding range of .2% concentration is (6~8)%RH.
it can be seen that when measuring a wide range of humidity, components with different concentrations must be used together. The number of components of the hygrometer combination that can be used for full-range measurement is generally five. The measuring range of the lithium chloride hygrometer using the component combination method is usually (15~1)%RH, and some foreign products claim that its measuring range can reach (2~1)%RH.
HS111 humidity sensor adopts patented solid polymer structure, which has the characteristics of fast response time, high reliability and long-term stability, and does not need calibration for complete interchangeability.