Basics of Ceramic Humidity Sensor
Release time:
2024-10-02
The ceramic humidity sensor is composed of metal oxide ceramics, which can be divided into ion type and electronic type.
The ceramic humidity sensor is composed of metal oxide ceramics, which can be divided into ion type and electronic type.
Ionic humidity sensor is a porous ceramic element made of insulating materials. Due to the physical adsorption of water molecules in micropores, H+appears in wet air, which increases the conductivity of the element. The main components are divided into two types α- Fe2O3, K2CO3 and ZnO.V2O5.LI2O.
The resistance of the ceramic humidity sensor varies greatly with the humidity resistance value in the low humidity section. In the range of 40% - 80% RH, the linearity is relatively good, while in the high humidity section, the change is too small. It can be seen that the ceramic humidity sensor has a good characteristic curve in the normal humidity state, while in the high humidity section, the curve in the low humidity section is distorted, and the nonlinearity is obvious. The humidity sensing characteristics of ceramic humidity sensors are also affected by temperature changes, and temperature compensation is important to the measurement accuracy.
Electronic humidity sensors mainly include the increase and decrease of conductivity of alumina and magnesium oxide composite ceramic humidity sensor elements, which are made by chemical adsorption of molecules on the oxide surface. N-type semiconductor and P-type semiconductor oxides react with positive humidity characteristics and negative humidity characteristics.
Aluminum oxide and magnesium oxide humidity sensors can measure humidity at temperatures below 700 ℃ and are relatively stable. However, due to the complex structure, the grating needs to be heated to 700 ℃, which consumes a lot of power and is expensive. It is also difficult to use in the industrial field because of the harsh use conditions and the need to prevent the characteristics from changing due to the change of air velocity.
Ceramic humidity sensor is a new type of sensor developed vigorously in recent years. The advantages are that the humidity lags behind, the response speed is fast, the volume is small, and it is convenient for batch production. However, due to the porous material, it has a great impact on the dust, and the daily maintenance is frequent. It often needs to be cleaned by electric heating, which easily affects the product quality and is vulnerable to humidity. In the low humidity and high temperature environment, the linearity is poor, especially the short service life and poor long-term reliability, which are the urgent problems for such humidity sensors to solve.
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