The temperature and humidity sensor is only one of the sensors. It only passes the temperature and humidity in the air through a certain detection device. After measuring the temperature and humidity, it is converted into an electrical signal or other required form of information output according to a certain rule to satisfy the user demand.
Since temperature and humidity are closely related to the physical quantity itself or the actual people's lives, the temperature and humidity integrated sensor will be generated accordingly. The temperature and humidity sensor refers to a device or device that can convert the amount of temperature and humidity into an electrical signal that is easily measured and processed. Temperature and humidity sensors on the market generally measure the amount of temperature and the amount of relative humidity.
1Select the measurement range
As with measuring weight and temperature, the humidity sensor is selected first to determine the measurement range. In addition to meteorological and scientific research departments, temperature and humidity measurement and control generally do not require full wet range (0-100% RH) measurement.
2Select measurement accuracy
Measurement accuracy is the most important indicator of the humidity sensor. For every 5% increase, it is the last step for the humidity sensor, or even the previous grade. Because of the different precisions, the manufacturing costs vary greatly, and the selling price is far from the same. Therefore, users must tailor their clothes, and they should not blindly pursue "high, precise, and sharp." If the humidity sensor is used at different temperatures, the indication will also take 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. In most cases, the accuracy of ±5% RH is sufficient if there is no precise temperature control or if the space being tested is unsealed. For areas requiring precise control of constant temperature and constant humidity, or where it is necessary to track and record humidity changes at any time, select a humidity sensor with an accuracy of ±3% RH or higher. The requirement that the accuracy is higher than ±2% RH may be difficult to achieve even the standard humidity generator of the calibration sensor, not to mention the sensor itself. Relative humidity measuring instruments, even at 20-25 ° C, to achieve 2% RH accuracy is still very difficult. The characteristics given in the general product data are measured at room temperature (20 ° C ± 10 ° C) and clean gas.
3 Consider time drift and warm drift
In actual use, due to the influence of dust, oil and harmful gases, the electronic humidity transmitter will age and the accuracy will decrease. The annual drift of the electronic humidity sensor is generally about ±2% or even higher. . Under normal circumstances, the manufacturer will indicate that the effective use time of one calibration is 1 year or 2 years, and it needs to be recalibrated when it expires.
4 Other precautions
The humidity sensor is non-sealing. To protect the accuracy and stability of the measurement, it should be avoided in acidic, alkaline and organic solvent-containing atmospheres. Also avoid use in dusty environments. In order to correctly reflect the humidity of the space to be tested, you should also avoid placing the sensor at a corner that is too close to the wall or where the air does not circulate. If the room being tested is too large, multiple sensors should be placed. Some humidity sensors have higher requirements on the power supply, otherwise the measurement accuracy will be affected. Or the sensors interfere with each other and can't even work. When using, the power supply with appropriate accuracy and accuracy should be provided according to the technical requirements. When the sensor needs to transmit long-distance signals, pay attention to the signal attenuation problem. When the transmission distance exceeds 200m, it is recommended to use the humidity sensor of the frequency output signal.
There are many kinds of temperature and humidity sensors on the market. From the output method, there are 485 communication, voltage type and current type. You can see the skill target parameters just like the same, which brings confusion to the customers. Pick a sensor? Summarize the following points for your reference:
First, Look at the company. See if a company is professional and see if the company has made a difference in the position and skills of the profession. Xiangxiang has always been focusing on the field of sensing measurement and control. Starting from the development of liquid leak detection products, it has continuously developed various intelligent detection equipments and sensors, and its experience and skills are relatively mature.
Second, look at the function. Measurement accuracy is an important target of humidity sensors, and the main factors affecting accuracy depend on the selected chips. Sensor chips with different precisions, different brands and different acquisition channels have different functions and their prices are far apart. The temperature and humidity sensor developed by the company is the SHT2X probe, which is the main product of the sensor brand Sheng Sirui. It has higher accuracy and stability than similar products.
Third, look at the function. Following the intensification of market competition and the further development of technology, brands have continuously added the functions of products in order to increase the competitiveness of their products. From the original no display to the LCD display; from 485 wired communication to wireless communication, etc.; customers should be clear about what their needs are. Nowadays, some of the additional functions of many products are actually not of much use, but instead have an impact on the basic and important precision and accuracy.
Four,Look at the structure. The structure of a good product is both compact and beautiful in appearance; it is also easy to produce and low in cost. The wiring method of temperature and humidity of most manufacturers is generally terminal type, and the wiring on site is a very troublesome thing. The temperature and humidity sensor developed by our company not only has LCD liquid crystal display, but also the wiring method is planned to be optional for the network port wiring and terminal wiring, which makes the wiring simple and easy. The details reflect the degree of care of the manufacturer.
Five,look at skills and services. A look at the provided skills support skills support can help users to agilely deal with problems encountered at the site, greatly saving the user's protection costs. Second, see if the after-sales service is timely, and whether the product repair is convenient and convenient.
If you have any questions about the selection of temperature and humidity sensors, please feel free to contact us.