As a key device for environmental monitoring, the measurement accuracy of temperature and humidity sensors directly affects the reliability of experimental data and industrial control effectiveness. Regular calibration is the core link to ensure the performance of sensors, and it is necessary to achieve value traceability through scientific methods and professional operations. The following is an analysis of the standardized calibration process and technical points:

1、 Preparation before calibration

It is crucial to choose standard instruments that have been certified for metrology. Common standards include: ① high-precision constant temperature and humidity chamber (temperature deviation ≤± 0.5 ℃, humidity deviation ≤± 2% RH); ② Saturated salt solution system (such as NaCl saturated solution corresponding to 75% RH); ③ Dew point meter (used for low-temperature humidity calibration). The sensors to be calibrated need to be preheated with electricity for 30 minutes in advance to eliminate the influence of mechanical stress on sensitive components. Prepare a record table to indicate equipment numbers, calibration times, and standard information, and establish a complete traceability file.

2、 Temperature calibration implementation

Place the sensor in the center area of the constant temperature and humidity chamber, keeping the probe vertically suspended to avoid radiation interference from the wall of the chamber. Adopting the step heating method: Starting from the low operating temperature, gradually increase to the highest operating temperature at intervals of 5 ℃, and record the readings after each temperature point stabilizes for 15 minutes. Focus on the deviation of typical temperature points such as 0 ℃, 25 ℃, and 40 ℃. If using a dry well furnace for high temperature calibration, an anti scald sheath should be installed to protect the sensor housing. During the calibration process, continuously monitor the displayed value of the standard instrument. If the measured value fluctuates beyond the allowable error range, immediately terminate and investigate issues such as poor circuit contact.

3、 Key points for humidity calibration

Humidity calibration requires distinguishing between relative humidity (% RH) and absolute humidity (g/m ³). When performing dynamic calibration in a constant temperature and humidity chamber, the temperature should be stabilized at 25 ℃ first, and then the humidity should be adjusted to the target value. Due to the strong hysteresis of humidity response, each calibration point needs to be stable for more than 60 minutes. For hair or capacitive sensors, double pressure method can be used for cross validation: place the sensors in high humidity (80% RH) and low humidity (30% RH) environments respectively, and observe whether the hysteresis loop is closed. When using a salt solution for calibration, it is necessary to ensure that the solution is thoroughly stirred and kept in a closed container to prevent external moisture from entering and affecting the concentration.

4、 Data correction and confirmation

After collecting at least 5 sets of valid data, calculate the average deviation between the sensor readings and the standard values. If the deviation exceeds the allowable range (usually temperature ± 0.5 ℃, humidity ± 3% RH), linear compensation or multi-point fitting correction should be performed through the upper computer software. After recalibration, recalibration verification is required, especially for testing stability under special temperature and humidity conditions. For intelligent sensors with digital output interfaces, the accuracy of data transmitted by MODBUS protocol can be synchronously verified.

5、 Special scenario handling

For pipeline mounted sensors, it is necessary to simulate actual working conditions for on-site calibration, with a focus on examining the impact of airflow velocity on measurement. Explosion proof sensors should be indirectly calibrated using simulated gas within a safe area. Wireless transmission devices require additional detection of measurement deviations caused by signal delays. After each calibration is completed, paste a new qualified label and update the equipment ledger, indicating the next calibration deadline.

The calibration of temperature and humidity sensors must strictly follow the national metrological verification regulations, combined with the technical parameters in the equipment manual. Through standardized operating procedures and scientific data processing, measurement uncertainty can be minimized, providing reliable environmental monitoring basis for scientific research, production, and quality management.