Module Temperature and Humidity Sensor DHT11 DHT-11 | Компьютеры и офис

Module Temperature and Humidity Sensor DHT11 DHT-11 | Компьютеры и офис

Digital temperature and humidity sensor
Because of the temperature and humidity, whether from the physical quantity itself or in the actual life of people have a close relationship, so the temperature and humidity of the sensor will be a corresponding. A temperature and humidity sensor is a device or device that converts temperature and humidity into electrical signals that can be easily measured. Temperature and humidity sensors on the market are generally measured temperature and relative humidity.
Temperature: the physical quantity of an object, which is one of the 7 basic physical quantities in the international system of units. In the production and scientific research, many physical phenomena and chemical processes are carried out at a certain temperature.
Humidity: a long time ago, there was a close relationship between life and humidity, but it was difficult to express in terms of quantity. The method for the calculation of humidity is the ratio of absolute humidity, relative humidity, dew point, moisture to dry gas (weight or volume) and so on. The most commonly used in daily life to express the physical quantity of humidity so that the relative humidity of the air.  Use%RH to express. There is a close relationship between relative humidity and temperature in the derivation of physical quantities. The higher the relative humidity, the lower the temperature, the higher the relative humidity. Complex thermal engineering knowledge.
The relationship between temperature and humidity and people's life:
For example: the winter temperature is 18 to 25 degrees centigrade, the humidity is from 30% to 80%; the temperature in summer is from 23 to 28 DEG C, and the humidity is from 30% to. People who feel comfortable in this area account for more than 95%. In air-conditioned room, room temperature of 19 to 24 degrees C, humidity of 40% to 50%, people will feel the most comfortable. If considering the temperature and humidity
The most suitable room temperature should be high working efficiency. 18 degrees, humidity should be between 40% to 60%, at this time, people's mental state is good, the most agile thinking.
Some definitions of humidity:
Relative humidity: in the measurement method, the humidity is defined as the amount of the physical state". Daily life refers to the relative humidity, with RH%. In a word, the percentage of saturated water vapor (saturated vapor pressure) in a gas (usually in the air) with the same amount of water vapor (water vapor pressure) as it is in the air.
Absolute humidity: refers to the water vapor amount per unit volume of the air in the actual content, generally in grams. Temperature has a direct impact on the absolute humidity, under normal circumstances, the higher the temperature, the more water vapor, the greater the absolute humidity; on the contrary, the absolute humidity is small.
Saturated humidity: the maximum amount of water vapor per unit volume, which can be contained in the air at a given temperature. If more than this limit, the excess water vapor will condense into water droplets, air humidity at this time is called saturated humidity. The humidity of the air is not constant, it changes with the change of temperature. The higher the temperature, the more water vapor can be contained in the unit volume of air, the greater the saturated humidity.
The dew point: that contains a certain amount of water vapor (absolute humidity) air, water vapor will contain when the temperature dropped to a certain degree of saturation (saturated humidity) and liquefied into water, this phenomenon is called.  The temperature at which water vapor begins to liquefy is called the dew point temperature". If the temperature continues to drop below the dew point, the saturated water vapor condenses into water droplets on the surface of the object.  In addition, the wind and air temperature and humidity are closely related, but also affect the temperature and humidity of the air is one of the important factors.
Temperature and humidity sensor selection considerations:
Select the measuring range
And the measurement of weight, temperature, humidity sensor to determine the first measurement range. In addition to meteorology, the Ministry of science and technology, the temperature and humidity measurement and control generally do not require full wet path (0-100%RH) measurement. Selection of measurement accuracy
Measurement accuracy is the most important indicator of humidity sensors, each increase of one percentage point, the humidity sensor is the last step, or even on a grade. Because to achieve a different accuracy, its manufacturing costs vary greatly, the price is also far. So the user must cut, not the blind pursuit of "high, fine, ". Such as the use of humidity sensors at different temperatures, the value of the temperature drift is also considered. As is known to all, relative humidity is a function of temperature, which severely affects the relative humidity in a given space. The temperature varies from 0.1 DEG C. Humidity variation (0.5%RH) will be generated. If it is difficult to make use of the constant temperature, it is not appropriate to put forward the high accuracy. In most cases, if there is no precise temperature control means, or the measured space is non sealed, the accuracy of the 5%RH is sufficient. For accurate control of constant temperature, humidity of local space, or need to keep track of changes in the recording of humidity, and then select more than 3%RH accuracy of humidity sensor. And the accuracy is higher than the requirements of the 2%RH or even calibration sensor standard humidity generator is difficult to do, not to mention the sensor itself. Relative humidity measuring instrument, even at 20 - 25 DEG C, to achieve the accuracy of 2%RH is still very difficult. The characteristics of the product are usually measured at room temperature (20 DEG C + + 10 C) and clean gas.
Time drift and Wen Piao
In actual use, due to the influence of dust, greasy dirt and harmful gas, used for a long time, the electronic humidity sensor will produce aging, decrease in accuracy, the electronic humidity sensor drift year generally within 2% or even higher. Normally