Humidity sensor technology trend analysis - sensor, humidity sensor - Electrical industry

Humidity sensor technology trend analysis - sensor

, humidity sensor - Electrical industry

In the industrial and agricultural production, weather, environmental protection, national defense, scientific research, aerospace and other departments, we often need to measure and control humidity. However, in the conventional environmental parameters, the most difficult to accurately measure the humidity is a parameter. With wet and dry bulb hygrometer to measure humidity, or hair hygrometer method, already unable to meet the needs of the development of modern technology. This is because the measurement of humidity and more complex than measuring the temperature, the temperature is measured is independent, while the humidity is affected by Other Factors (atmospheric pressure, temperature) effects. In addition, standard humidity is a problem. Foreign production of humidity calibration equipment is high.

Recent years, at home and abroad in the humidity Sensor R & D has made great strides. Humidity Sensor Are from simple humidity sensor to the integrated, intelligent, multi-parameter detection of the direction of rapid development, for the development of a new generation of humidity / temperature control system to create favorable conditions will also humidity measurement to a new level.

1 Humidity Sensor features Humidity sensor humidity sensor is the simplest. Main resistive humidity sensor, capacitive two categories.

1.1 Humidity resistance Humidity resistance is characterized by a layer of the substrate material with a sense of the wet membrane, when the air humidity sensitive membrane vapor adsorption, the components of the resistivity and resistance values are changed, the use This feature can measure humidity. Humidity resistance of many types, such as humidity resistance characteristics of metal oxide, silicon humidity resistance, humidity resistance and other ceramics. Humidity resistance of the advantages of high sensitivity, linearity and the major drawback is poor interchangeability of products.

1.2 Humidity Capacitance Humidity capacitance is generally made of polymer film capacitors, polymer materials commonly used are polystyrene, polyimide, cellulose acetate acid and so cool. When the ambient humidity changes, the capacitance of the dielectric constant humidity changes, it also changes the capacitance, its capacitance is proportional to the change in relative humidity. The main advantage of capacitive humidity sensing with high sensitivity and good product interchangeability, response speed, humidity, lag is small, easy to manufacture, easy miniaturization and integration, the accuracy generally is lower than the humidity resistance. Humidity Capacitance main overseas production factories have Humirel company, Philips Company, Siemens Corporation. SH1100 manufactured by Humirel Humidity Capacitance-type example, the measurement range (1% ~ 99%) RH, at 55% RH when the power capacity of 180pF (typical value). When the relative humidity changes from 0 to 100%, the change in capacitance range is 163pF ~ 202pF. Temperature coefficient of 0.04pF / , humidity lag was 1.5%, a response time of 5s.

Addition to resistive, capacitive-type humidity sensor, there is electrolyte ionic humidity sensor, humidity sensor type weight (wet film using a sense of weight change to change the oscillation frequency), intensity-based humidity sensor, SAW humidity sensor and so on. Humidity sensor linearity and anti-pollution, poor relative humidity in the test, the humidity sensor to be tested long-term exposure in the environment, are easily affected by pollution, measurement accuracy and long-term stability.

2 integrated humidity sensor performance characteristics and product categories

Present, foreign production integrated humidity sensor of the major manufacturers and typical products in Honeywell Inc. (HIH-3602, HIH-3605, HIH-3610 type), Humirel Corporation (HM1500, HM1520, HF3223, HTF3223 type), Sensiron Company (SHT11, SHT15 type). These products can be grouped into three types:

2.1 linear voltage output type integrated humidity sensor

Typical products HIH3605/3610, HM1500/1520.

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