| In the industrial and agricultural production, weather, | | | | materials commonly used are polystyrene, polyimide, |
| environmental protection, national defense, scientific | | | | cellulose acetate acid and so cool. When the ambient |
| research, aerospace and other departments, we | | | | humidity changes, the capacitance of the dielectric |
| often need to measure and control humidity. | | | | constant humidity changes, it also changes the |
| However, in the conventional environmental | | | | capacitance, its capacitance is proportional to the |
| parameters, the most difficult to accurately measure | | | | change in relative humidity. The main advantage of |
| the humidity is a parameter. With wet and dry bulb | | | | capacitive humidity sensing with high sensitivity and |
| hygrometer to measure humidity, or hair hygrometer | | | | good product interchangeability, response speed, |
| method, already unable to meet the needs of the | | | | humidity, lag is small, easy to manufacture, easy |
| development of modern technology. This is because | | | | miniaturization and integration, the accuracy generally |
| the measurement of humidity and more complex | | | | is lower than the humidity resistance. Humidity |
| than measuring the temperature, the temperature is | | | | Capacitance main overseas production factories have |
| measured is independent, while the humidity is | | | | Humirel company, Philips Company, Siemens |
| affected by Other Factors (atmospheric pressure, | | | | Corporation. SH1100 manufactured by Humirel |
| temperature) effects. In addition, standard humidity is | | | | Humidity Capacitance-type example, the |
| a problem. Foreign production of humidity calibration | | | | measurement range (1% ~ 99%) RH, at 55% RH |
| equipment is high. | | | | when the power capacity of 180pF (typical value). |
| Recent years, at home and abroad in the humidity | | | | When the relative humidity changes from 0 to 100%, |
| Sensor R & D has made great strides. Humidity | | | | the change in capacitance range is 163pF ~ 202pF. |
| Sensor Are from simple humidity sensor to the | | | | Temperature coefficient of 0.04pF / , humidity lag |
| integrated, intelligent, multi-parameter detection of | | | | was ± 1.5%, a response time of 5s. |
| the direction of rapid development, for the | | | | Addition to resistive, capacitive-type humidity sensor, |
| development of a new generation of humidity / | | | | there is electrolyte ionic humidity sensor, humidity |
| temperature control system to create favorable | | | | sensor type weight (wet film using a sense of weight |
| conditions will also humidity measurement to a new | | | | change to change the oscillation frequency), |
| level. | | | | intensity-based humidity sensor, SAW humidity |
| 1 Humidity Sensor features Humidity sensor humidity | | | | sensor and so on. Humidity sensor linearity and |
| sensor is the simplest. Main resistive humidity sensor, | | | | anti-pollution, poor relative humidity in the test, the |
| capacitive two categories. | | | | humidity sensor to be tested long-term exposure in |
| 1.1 Humidity resistance Humidity resistance is | | | | the environment, are easily affected by pollution, |
| characterized by a layer of the substrate material | | | | measurement accuracy and long-term stability. |
| with a sense of the wet membrane, when the air | | | | 2 integrated humidity sensor performance |
| humidity sensitive membrane vapor adsorption, the | | | | characteristics and product categories |
| components of the resistivity and resistance values | | | | Present, foreign production integrated humidity |
| are changed, the use This feature can measure | | | | sensor of the major manufacturers and typical |
| humidity. Humidity resistance of many types, such as | | | | products in Honeywell Inc. (HIH-3602, HIH-3605, |
| humidity resistance characteristics of metal oxide, | | | | HIH-3610 type), Humirel Corporation (HM1500, |
| silicon humidity resistance, humidity resistance and | | | | HM1520, HF3223, HTF3223 type), Sensiron Company |
| other ceramics. Humidity resistance of the | | | | (SHT11, SHT15 type). These products can be |
| advantages of high sensitivity, linearity and the major | | | | grouped into three types: |
| drawback is poor interchangeability of products. | | | | 2.1 linear voltage output type integrated humidity |
| 1.2 Humidity Capacitance Humidity capacitance is | | | | sensor |
| generally made of polymer film capacitors, polymer | | | | Typical products HIH3605/3610, HM1500/1520. |