Development of humidity measurement and introduction of electronic humidity sensor method
Humidity measurement technology has been around for a long time. With the development of electronic technology, modern measurement technology has also developed rapidly. Humidity measurement is divided into two or thirty in principle. The means of expressing humidity are absolute humidity, relative humidity, dew point, moisture to dry gas ratio (weight or volume), and the like. But humidity measurement has always been one of the famous problems in the world of metrology. A seemingly simple measure of value, involving quite complex physics-chemical theoretical analysis and calculations, may involve many factors that must be noted in humidity measurement, thus affecting the rational use of the sensor.
Common methods of measuring humidity include: dynamic method (double pressure method, double temperature method, and split method): double pressure method and double temperature method are based on thermodynamic P, V, and T balance principles, and the equilibrium time is long. The shunt method is based on absolute Precise mixing of moisture and absolute dry air. Due to the adoption of modern measurement and control methods, these devices can be made quite sophisticated, but because of the complexity and cost of the equipment, the operation is time-consuming and labor-intensive, mainly used as a standard measurement, and its measurement accuracy can be more than ± 2%.
Static method (saturated salt method, sulfuric acid method): The saturated salt method is the most common method in humidity measurement, and it is simple and easy. However, the saturated salt method requires strict balance between liquid and gas phases, and requires high stability to ambient temperature. It is required to wait for a long time to balance, and the low humidity point is required to be longer. Especially when the indoor humidity and the difference in the humidity inside the bottle are large, it needs to be balanced for 6-8 hours each time.
Electronic Humidity Sensor Method: Electronic humidity sensor products and humidity measurement belong to the industry that emerged in the 1990s. In recent years, domestic and foreign companies have made great progress in the field of humidity sensor research and development. Humidity sensors are rapidly evolving from simple humidity sensors to integrated, intelligent and multi-parameter detection, creating favorable conditions for the development of a new generation of humidity measurement and control systems, and raising humidity measurement technology to a new level.
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. However, in conventional environmental parameters, humidity is one of the most difficult parameters to measure accurately. The method of measuring humidity with a wet and dry bulb hygrometer or a hair hygrometer has long been unable to meet the needs of modern technological development. This is because measuring humidity is much more complicated than measuring temperature, temperature is measured independently, and humidity is affected by other factors (atmospheric pressure, temperature). In addition, the standard of humidity is also a problem. The 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 sensors are rapidly evolving from simple humidity sensors to integrated, intelligent and multi-parameter detection, creating favorable conditions for the development of a new generation of humidity/temperature measurement and control systems, and raising humidity measurement technology to a new level.
The accuracy of the humidity sensor is segmented: the medium and low wet sections (0-80% RH) are ±2% RH, and the high-humidity section (80-100% RH) is ±4% RH. And this accuracy is at a specified temperature. The value under (eg 25 ° C). Use a humidity sensor at different temperatures. Its indication also takes into account the effects of temperature drift. It is well known that relative humidity is a function of temperature, which severely affects the relative humidity within a given space. The temperature changes by 0.1 °C. A humidity change (error) of 0.5% RH will be produced. In the case of use, if it is difficult to achieve constant temperature, it is not appropriate to propose excessive humidity measurement accuracy. Because the humidity is also erratic with temperature changes, the luxury measurement accuracy will lose its practical significance. Therefore, the first thing to control the humidity is to control the temperature. This is why a large number of applications are often temperature and humidity integrated sensors rather than pure humidity sensors.
As a professional online shopping mall, Shenzhen Gongcai.com has imported top-grade humidity sensors from abroad. Next, I will bring three humidity sensors with the same quality and performance.
French Humirel digital output temperature and humidity sensor HTU21D:
The new digital temperature and humidity composite sensor HTU21D sets a new model of humidity sensor size and intelligence: in a DFN package suitable for reflow soldering, measuring only 3 x 3 x 1mm; providing a corrected, linear I2C digital output signal. The HTU21D is a plug-and-play humidity and temperature composite sensor ideal for OEM applications that require reliable and accurate measurements. The humidity and temperature signals of the digital outputs can be interfaced directly to the microcontroller. Each sensor is calibrated and tested, and the lot number is printed not only on the housing but also on the sensor chip for reading by instruction. The user can change the resolution of the HTU21D (8/12bit to 12/14bit) by command. In addition, the sensor can detect low power and checksums are used to improve communication reliability. The HTU21D's low power consumption, high cost performance and small size make it suitable for OEM high volume applications where price sensitivity and installation space are limited. Used in engines and motor vehicles, medical, industrial control, consumer electronics and household appliances industries.
Digital temperature and humidity sensor HTU21D features:
1, fully interchangeable, no need to recalibrate
2. Rapid recovery after long-term saturation
3. Suitable for automated assembly methods such as lead-free reflow soldering
4, separate identification, in line with strict traceability requirements
French Humilel Humidity Sensor - HM1500LF:
The Humidity Sensor HM1500LF is a humidity probe based on the rugged HS1101LF sensing element designed for OEM applications that require reliable and accurate measurements. The product is small in size and easy to install. Linear voltage output for direct connection to the microcontroller. Used in industrial, process control, engines and motor vehicles.
Humidity sensor HM1500LF characteristics and technical parameters:
Small size
Lead-free, chromium and mercury
Humidity accuracy: ±2% @55%RH
1V ~ 3.6V DC output (0% ~ 100% RH @ 5Vdc power supply)
Supply voltage: 4.75Vdc ~ 5Vdc
Patented solid polymer structure
Good interchangeability
High reliability and long-term stability
Not affected by flooding
Low temperature dependence
Rapid recovery after long-term saturation
Quick response
Distillable water cleaning
French Humirel Capacitive Humidity Sensor - HS1101LF:
Capacitive humidity sensor HS1101LF is a capacitive relative humidity sensor. The humidity sensor HS1101/HS1101LF sensor is based on a unique process design of humidity sensitive capacitive components. Fully interchangeable, no calibration required in standard environments, fast dehumidification under long-term saturation, automatic soldering, including wave soldering, high reliability and long-term stability, patented solid polymer structure, can be used for linear voltage or Frequency output loop, fast response time. Suitable for high volume, low cost applications. Mainly used in temperature and humidity instruments, office automation, automotive cab air control, household appliances, industrial process control systems and other fields.
Capacitive humidity sensor HS1101LF features:
Lead-free
High reliability and long-term stability
Patented solid polymer structure
Suitable for linear voltage output or frequency output circuits
Fast response, low temperature coefficient
Good interchangeability, no need to recalibrate under standard conditions
Rapid recovery after long-term saturation
Suitable for automated assembly, including lead-free wave soldering and reflow soldering
Individual identification for easy traceability
Distillable water cleaning
Capacitive humidity sensor HS1101LF technical parameters:
Capacitor component based on unique process design, patented solid polymer structure
High precision: ±2% RH, excellent linear output
Wide range: 1~99% RH, wide operating temperature range –60~140°C (HS1101LF), –40~100°C (HS1101)
Humidity output is minimally affected by temperature, no temperature compensation is required for normal temperature use
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