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. What are the precautions in the selection of temperature and humidity sensors?
Selecting the temperature and humidity sensor has the following considerations:
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 widely, 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 measured 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 current output signal.
The future temperature and humidity sensor market has broad prospects especially in the fields of consumer electronics and the Internet of Things. The products of IC semiconductor temperature and humidity sensors with small size, low power consumption, low cost and high integration will be more popularized and applied.
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