Development trend of the hottest humidity sensor 1

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The development trend of humidity sensors

in industrial and agricultural production, meteorology, environmental protection, national defense, scientific research, aerospace and other departments, it is often necessary to measure and control the environmental humidity. But among the conventional environmental parameters, humidity is the most difficult to measure accurately. The method of measuring humidity with a new material experimental machine or hair hygrometer developed to meet people's safety needs has long been unable to meet the needs of the development of modern science and technology. This is because measuring humidity is much more complex than measuring temperature. Temperature is measured independently, while humidity is affected by other factors (atmospheric pressure, temperature)

in addition, the calibration of humidity is also a difficult problem. Humidity calibration equipment produced abroad is very expensive

in recent years, great progress has been made in the field of humidity sensor research and development 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 the development of a new generation of humidity/temperature measurement and control system, and also improves the humidity measurement technology to a new level

characteristics of humidity sensor

humidity sensor is the simplest humidity sensor. Humidity sensors are mainly divided into resistance type and capacitance type

a humidity sensitive resistor

the characteristic of humidity sensitive resistor is that the substrate is covered with a film made of humidity sensitive material. When the water vapor in the air is adsorbed on the humidity sensitive film, the resistivity and resistance value of the element change. Using this characteristic, humidity can be measured. There are many kinds of humidity sensitive resistors, such as metal oxide humidity sensitive resistors, silicon humidity sensitive resistors, ceramic humidity sensitive resistors, etc. The advantage of humidity sensitive resistor is high sensitivity, and the main disadvantage is poor linearity and interchangeability of products

b humidity sensitive capacitance

humidity sensitive capacitance is generally made of polymer film capacitance. Commonly used polymer materials include polystyrene, polyimide, butyric acid acetate fiber, etc. When the environmental humidity changes, the dielectric constant of the humidity sensitive capacitance changes, so that its capacitance also changes, and its capacitance change is directly proportional to the relative humidity. The main advantages of humidity sensitive capacitor are high sensitivity, good product interchangeability, fast response speed, small humidity hysteresis, easy to manufacture, easy to realize miniaturization and integration, and its accuracy is generally lower than that of humidity sensitive resistor. The main manufacturers of humidity sensitive capacitors abroad include Humirel company, Philips company, Siemens company, etc. Taking the sh1100 humidity sensitive capacitor produced by Humirel company as an example, its measurement range is (1% ~ 99%) RH, and the capacitance at 55% RH is 180 PF (typical value) in terms of investment. When the relative humidity changes from 07.3 to 100% in batches, the variation range of capacitance is 163pf ~ 202pf. The temperature coefficient is 0.04pf/℃, the humidity hysteresis is ± 1.5%, and the response time is 5S

in addition to resistive and capacitive humidity sensors, there are electrolyte ion humidity sensors, which calculate the maximum zigzag stress at the cross section of the load, weight humidity sensors (using the change of the weight of the humidity sensing film to change the oscillation frequency), light intensity humidity sensors, surface acoustic wave humidity sensors, etc

the linearity and pollution resistance of the humidity sensor are poor. When detecting the environmental humidity, the humidity sensor should be exposed to the environment to be measured for a long time, which is easy to be polluted and affect its measurement accuracy and long-term stability

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