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Temperature and humidity sensor measurement considerations

First, select the range of measurements

As with measuring weight and temperature, the first choice of humidity sensor is to determine the range of measurement. Apart from meteorological and scientific research departments, temperature and humidity measurement and control generally do not need the full wet range of 0-99.9 RH measurements.

Second, select measurement accuracy

Measurement accuracy is the most important indicator of humidity sensors. Every increase of one percent is a step up or even a step up to a humidity sensor. Because to achieve different accuracy, the manufacturing costs vary greatly. The price is also very different. Therefore, users must tailor their clothes, not blindly pursue "high, fine, sharp." if humidity sensors are used at different temperatures, their indication also takes into account the effect of temperature drift. As we all know, Relative humidity is a function of temperature, which seriously affects the relative humidity in a given space. Each change in temperature of 0.1 ℃ will result in a humidity change of 0.5%RH. In most cases, if there is no precise temperature control means or the measured space is unsealed, the accuracy of ±5%RH is sufficient. Or if you need to track and record humidity changes at any time, then choose a humidity sensor with a precision of ±3%RH or above. And if the accuracy is higher than ±2%RH, it may be difficult to even calibrate the standard humidity generator of the sensor. Moreover, the sensor itself. It is difficult to achieve the accuracy of 2%RH even at 20-25 ℃. The characteristics given in the product data are usually measured in normal temperature (20 ℃ ±10 ℃) and clean gas.

Third, considering time drift and temperature drift

In practical use, due to the influence of dust, oil and harmful gases, the electronic humidity transmitter will produce aging and decrease in accuracy when it is used for a long time. The annual drift of the electronic humidity sensor is generally ±2%. Generally, the manufacturer indicates that the effective use time of one calibration is 1 year or 2 years, due to be re-calibrated.

Other points for attention

The humidity sensor is unsealed. To protect the accuracy and stability of the measurement, the acidity should be avoided as far as possible. Used in alkaline and organic solvent atmosphere. Also avoid use in dusty environment. To correctly reflect the humidity of the space to be measured, You should also avoid placing sensors in dead corners that are too close to the wall or where air is not well ventilated. If the room under test is too large, multiple sensors should be placed. Some humidity sensors require higher power supply. Otherwise, the measurement accuracy will be affected. Or the sensors will interfere with each other, or even cannot work. In use, the power supply should be provided in accordance with the technical requirements. When the sensor needs to carry out long-distance signal transmission, the power supply should be provided in accordance with the technical requirements. Attention should be paid to the attenuation of signals. When the transmission distance is more than 200 m, the humidity sensor of the frequency output signal is recommended.