How to choose Best temperature and humidity sensor

Select measuring range

Just like measuring weight, temperature, and humidity, when choosing a temperature and humidity sensor, you must first determine the measurement range. Except for meteorological and scientific research departments, high temperature and humidity measurement and control generally do not require full humidity range (0-100% RH) measurement.

Select measurement accuracy

The measurement accuracy is the most important indicator of the temperature and humidity sensor. Every percentage point improvement means that the temperature and humidity sensor reaches a higher level, or even a higher level. Because to achieve different precisions, their manufacturing costs vary greatly, and their selling prices also vary widely. Therefore, users must tailor their products to suit their needs and should not blindly pursue “high, precise, and cutting-edge”.

If the humidity sensor is used at different temperatures, the influence of temperature drift should also be considered on its indication value. It is well known that relative humidity is a function of temperature, and temperature strongly affects relative humidity in a given space. Every time the temperature changes by 0.1°C. A humidity change (error) of 0.5% RH will occur. If it is difficult to maintain a constant temperature in the usage situation, it is inappropriate to propose too high humidity measurement accuracy.

In most cases, if there is no precise temperature control method, or the measured space is not sealed, an accuracy of ±5% RH is sufficient. For local spaces that require precise control of constant temperature and humidity, or where humidity changes need to be tracked and recorded at any time, a temperature and humidity sensor with an accuracy of ±3% RH or above is selected.

The requirement of accuracy higher than ±2% RH may be difficult to achieve even with the standard humidity generator used to calibrate the sensor, let alone the sensor itself. For relative temperature and humidity measuring instruments, it is still very difficult to achieve an accuracy of 2% RH even at 20-25°C. Usually the characteristics given in the product data are measured at normal temperature (20℃±10℃) and in clean gas.

Consider time drift and temperature drift

In actual use, due to the influence of dust, oil and harmful gases, the electronic humidity sensor will age and the accuracy will decrease over time. The annual drift of the electronic temperature and humidity sensor is generally around ±2%, or even higher. Under normal circumstances, the manufacturer will indicate that the effective use time of a calibration is 1 or 2 years, and recalibration is required upon expiration.