When calibrating hygrothermographs, the following points should be noted:
I. Environmental factors
Stable environment: Select a stable environment for calibration and avoid places with large fluctuations in temperature and humidity. For example, do not calibrate near windows, air conditioning outlets, or heat sources, as the temperature and humidity change rapidly in these places, which will affect the accuracy of calibration.
No interference sources: Ensure that there are no interference sources such as electromagnetic fields and vibrations in the calibration environment. Electromagnetic fields may interfere with the measurement of electronic hygrothermographs, and vibrations may affect the accuracy of mechanical hygrothermographs.
II. Selection of standard equipment
Precision and accuracy: Select standard equipment with high precision and accuracy for calibration. The precision of the standard equipment should be at least one order of magnitude higher than that of the hygrothermograph to be calibrated to ensure the reliability of calibration.
Calibration certificate: Ensure that the standard equipment has a valid calibration certificate, which should indicate the calibration date, calibration institution, calibration method, and calibration results.
Applicability: According to the measurement range and accuracy requirements of the hygrothermograph to be calibrated, select appropriate standard equipment. For example, if the measurement range of the hygrothermograph to be calibrated is -20°C to 60°C and the relative humidity is 10% to 90%, then standard equipment with a measurement range and accuracy that can cover this range should be selected.
III. Operating specifications
Warm-up time: Before calibration, ensure that both the hygrothermograph and the standard equipment have sufficient warm-up time. Generally, electronic hygrothermographs need to be warmed up for 15 to 30 minutes, and mechanical hygrothermographs need to be warmed up for 30 minutes to 1 hour.
Placement position: Place the hygrothermograph and the standard equipment in the same position to ensure that they are affected by the same temperature and humidity. If possible, use a bracket to fix them at the same height to avoid the influence of position differences on the measurement results.
Reading time: When reading the readings of the hygrothermograph and the standard equipment, wait for sufficient time to ensure that the readings are stable. Generally, the reading stability time of electronic hygrothermographs is shorter, about a few seconds to a few minutes, while the reading stability time of mechanical hygrothermographs is longer, which may take several minutes to more than ten minutes.
Repeated measurements: To improve the accuracy of calibration, multiple repeated measurements can be performed and the average value can be taken as the final calibration result. The number of repeated measurements should be determined according to the actual situation. Generally, at least three repeated measurements should be performed.
IV. Data recording and processing
Record complete information: During the calibration process, complete calibration information should be recorded, including the model, number, measurement range, accuracy requirements, calibration date, calibration environment, model and number of standard equipment, calibration certificate number, measurement results, and other information.
Data processing method: According to the calibration results, an appropriate data processing method is used for analysis and judgment. If the calibration results exceed the allowable error range, adjustments or repairs should be made and calibration should be performed again. Common data processing methods include comparison method, difference method, regression analysis method, etc.
V. Maintenance and care
Regular calibration: To ensure the accuracy of the hygrothermograph, calibration should be performed regularly. The calibration cycle should be determined according to factors such as the usage frequency, accuracy requirements, and environmental conditions of the hygrothermograph. Generally, high-precision hygrothermographs have a shorter calibration cycle, about half a year to one year, while low-precision hygrothermographs have a longer calibration cycle, about one to two years.
Cleaning and maintenance: Clean the housing and sensor of the hygrothermograph regularly to avoid the influence of dust, dirt, and moisture on the measurement results. At the same time, pay attention to protecting the sensor of the hygrothermograph to avoid collisions and damages. If the hygrothermograph malfunctions or is damaged, it should be repaired or replaced in time.
