Why do temperature and humidity sensors have deviations?

| Principle of operation

Temperature and humidity sensors are devices that detect and convert changes in temperature and humidity into electrical signals. Temperature sensors typically use thermistors or thermal couplers to convert temperature into resistance or voltage changes. Humidity sensors, such as capacitive sensors. It utilizes changes in humidity to cause changes in the capacitance value of the medium. 

By converting this to an electrical signal through amplification and processing, the temperature and humidity values can be displayed or output. Different types of sensors have different sensing principles, but the basic idea is to sense the parameters and convert them into measurable electrical signals. The performance of the sensor depends on the accuracy of the design of the conversion circuit.

| Factors affecting sensor accuracy

1. Environmental conditions

If the temperature and humidity conditions of the use environment if beyond the applicable range of the sensor design. This will directly affect the sensing performance. For example, the use of humidity sensors in low humidity or high humidity conditions, will make the accuracy decline. High temperatures will also change the performance parameters of the sensor's sensitive components. In addition, corrosive gas pollution will also reduce the sensor sensitivity. So reasonable selection of sensors, and control the use of the environment in the appropriate range, can improve accuracy.

2、Sensing element aging

Due to long term usage, temperature and humidity sensors will gradually occur in the sensor element aging. This leads to the sensor parameters drift and change, making the test results bias. For example, the resistance value of the thermistor will gradually increase, moisture-sensitive media will change the moisture absorption characteristics. Regular maintenance and calibration must be carried out to compensate for the decline in accuracy caused by aging.

3、Process error

Because it is difficult to completely eliminate tolerance errors in the manufacturing process, there must be a slight deviation of the sensor parameters between individuals, which will make the initial accuracy affected. But can be eliminated through comparative testing of products with excessive deviation, and calibration calibration in use to improve accuracy.

| Improper installation and use

1、Inappropriate location

First, the temperature and humidity sensor installation location needs to ensure that the temperature and humidity of the measured environment can be effectively collected. If the installation location is not selected properly, the environmental parameters can not be sampled effectively. Therefore, it will lead to measurement errors. For example, the humidity sensor contact with the outside air is not enough, or temperature sensors by other equipment heat impact, will make the monitoring data distortion.

2、Line interference

Second, the signal line problems also affect the accuracy. Weak sensing signals, if electromagnetic interference, will produce noise and lead to deviation in the results. Correct wiring and the use of shielded wires or differential signaling can improve interference resistance. Signal acquisition circuit design also needs to ensure high common mode rejection ratio, filtering noise.

3、Failure to calibrate on time

Finally, long-term use of the process, do not carry out regular calibration and calibration will also make the sensor drift. Regularly back to school compared to the standard, can compensate for aging drift, greatly improving the long-term stability of the measurement system. Incorrect calibration methods can also introduce new errors. The environmental conditions and methods of calibration need to follow standard specifications.

| Friendly suggestions

1、Sensor Selection

From the sensor design and manufacturing, you can choose high stability, high precision sensor products. High-quality sensors in the selection of components, circuit design and packaging technology is more precise, can make the accuracy to meet the target requirements. And choose the sensing range and the use of environmental matching products. Reasonable selection is the first step to improve the accuracy of the system.

2、 Sensors Usage

From the use of the sensor needs to be reasonably arranged to avoid external interference. Control the temperature and humidity of the working environment within the applicable range, to reduce the temperature and humidity fluctuations on the accuracy of the impact. And the establishment of regular calibration and back-to-calibration mechanism to ensure the accuracy of the long-term use of the process. At the same time, regular cleaning and maintenance is also needed to prevent the impact of pollution on the measurement.