The temperature and humidity sensor is only one of the sensors, which only measures the temperature and humidity in the air through a certain detection device, and then converts it into an electrical signal or other required form of information output according to a certain law to meet the needs of users.
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Since temperature and humidity are closely related to both the physical quantity itself and the actual life of people, the sensor integrating temperature and humidity will be produced accordingly. A temperature and humidity sensor is a device or device that converts temperature and humidity into electrical signals that can be easily measured and processed. Temperature and humidity sensors on the market generally measure the amount of temperature and relative humidity.
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1. Select the measurement accuracy
The selection of temperature and humidity sensors is based on the measurement accuracy is the most important indicator of the humidity sensor, and every one percentage point increase is a step or even a grade for the humidity sensor. Because to achieve different precisions, the manufacturing cost varies greatly, and the selling price varies greatly. Therefore, users must be tailor-made, and should not blindly pursue “high, refined, and sharp”. If a humidity sensor is used at different temperatures, the effect of temperature drift should also be taken into account in the indication value.
As we all know, relative humidity is a function of temperature, and temperature has a significant impact on the relative humidity in a given space. Every 0.1°C change in temperature. A humidity change (error) of 0.5%RH will be generated. If it is difficult to achieve constant temperature in the use case, it is not appropriate to propose too high humidity measurement accuracy. In most cases, if there is no precise means of temperature control, or if the measured space is unsealed, an accuracy of ±5%RH is sufficient.
For local spaces that require accurate control of constant temperature and humidity, or where it is necessary to track and record humidity changes at any time, a humidity sensor with an accuracy of ± 3% RH or more is selected. The requirement for an accuracy higher than ±2%RH is difficult to achieve even with a standard humidity generator that calibrates the sensor, let alone the sensor itself.
Even at 20-25°C, it is difficult to achieve an accuracy of 2%RH. Usually the properties given in the product literature are measured at room temperature (20°C±10°C) and in a clean gas.
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2. Consider time drift and temperature drift:
In actual use, due to the influence of dust, oil and harmful gases, after a long period of use, the electronic humidity sensor will age, the accuracy will decrease, and 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 the first calibration is 1 or 2 years, and the calibration needs to be re-calibrated when it expires.
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3. Select the measurement range:
The selection of temperature and humidity sensors is based on the same as the measurement of weight and temperature, and the selection of humidity sensors should first 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 (0-99.9%RH) measurement.
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4. Other precautions:
Humidity sensors are non-hermetically sealed, and in order to protect the accuracy and stability of the measurement, they should be avoided in acidic, alkaline and organic solvent-containing atmospheres. It is also avoided to use in dusty environments.
To accurately reflect the humidity of the space to be measured, avoid placing the sensor too close to a wall or in a dead corner where there is no air circulation. If the room to be measured is too large, multiple sensors should be placed. Some humidity sensors have high requirements for power supply, otherwise the measurement accuracy will be affected.
Sometimes the sensors interfere with each other and even fail to work. When using, a suitable power supply should be provided in accordance with the technical requirements and meet the accuracy requirements. When the sensor needs to transmit signals over long distances, it is necessary to pay attention to the attenuation of the signal. When the transmission distance is more than 200m, it is recommended to use a humidity sensor with a frequency output signal.
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