Temperature and humidity are physical quantities of cold and hot objects. As important standards for measuring overall environmental quality, many physical phenomena and chemical processes in production and scientific research occur under specific temperature and humidity conditions. The demand for temperature and humidity sensors is increasing in fields such as agriculture, industry, buildings, offices, and computer rooms.
A temperature and humidity sensor is a sensor device equipped with humidity-sensitive and temperature-sensitive elements, used to measure temperature and humidity. It converts temperature and humidity measurements into easily measurable and processable electrical signals. In today's highly developed scientific and technological landscape, the demand for measurement accuracy is increasingly high; therefore, reducing or eliminating sensor errors caused by temperature is particularly important. However, when using temperature and humidity sensors, it is sometimes observed that they drift after a period of use.
Temperature and humidity sensor drift is divided into zero-point drift and temperature drift. These two types of drift have different effects on the measurement accuracy of the sensor. The sensor detects some external parameters and then transmits some analog and digital signals. Due to some interference from the external environment, the signal transmitted by the sensor is mixed with some interference signals. How to solve sensor drift is very important.
In actual use, due to the influence of dust, oil and harmful gases, the temperature and humidity sensor will age and become less accurate over time. The annual drift of the temperature and humidity sensor is generally around ±2%. Under normal circumstances, the manufacturer will indicate that the effective service time of one calibration is 1 or 2 years, and recalibration is required after the expiration.
Why do temperature and humidity sensors drift after a period of time?
1. Temperature and humidity sensors will drift during use, and this phenomenon is unavoidable.
2. The root cause of drift is that all pressure sensors are based on the elastic deformation of a material. No matter how good the elasticity of the material is, after each elastic recovery, a certain amount of elastic fatigue will always occur.
3. During the use of temperature and humidity sensors, the drift caused by elastic materials varies depending on the material, but as long as it is a qualified product, it is within a very small range.
4. Besides material-induced drift, there is a more significant type of drift: temperature drift. Temperature drift generally refers to the changes in transistor parameters caused by variations in ambient temperature. This can lead to instability in the static operating point, unstable dynamic parameters of the circuit, and even malfunction of the circuit. In amplifier circuits, any change in parameters, such as fluctuations in power supply voltage, component aging, or changes in semiconductor component parameters with temperature, will cause output voltage drift.
5. In addition to the drift factors mentioned above, the drift of temperature and humidity sensors also depends on the circuit design and the quality of the components.
6. Temperature and humidity sensors rarely drift if used for a long time, but if left in reserve for an extended period, the probability of temperature drift is relatively high.
So how can we resolve the errors caused by the offset of the temperature and humidity sensor?
In temperature and humidity sensors, under otherwise constant conditions, the output signal drifts with temperature changes. To mitigate this, algorithms are used to correct the output, eliminating the influence of temperature variations on the signal within a certain range. This method is called temperature compensation for temperature and humidity sensors, or simply "temperature compensation." Currently, most temperature and humidity sensors incorporate temperature compensation to ensure accurate temperature and humidity monitoring within a defined range.
