I. Laboratory-grade High-precision Calibration (Suitable for Legal Metrology and High-precision Production Scenarios)

1. Standard Thermostatic Bath Calibration Method (Most Commonly Used)
   • Core Principle: A standard thermostatic bath is used to provide a stable and uniform constant temperature environment. The sensor of the tester to be calibrated and a higher-precision standard thermometer (e.g., a secondary standard platinum resistance thermometer) are placed in the constant temperature zone of the bath simultaneously. The error is calculated by comparing the readings of the two devices.
   • Key Operational Points:
     • Select a thermostatic bath with a range covering that of the tester (e.g., -50℃ to 600℃). The medium in the bath should be selected according to the temperature range, such as silicone oil (for medium and high temperatures) and ethanol (for low temperatures).
     • Select 3–5 calibration points (e.g., 0℃, 25℃, 100℃, 300℃, 500℃). For each point, record data after maintaining a constant temperature for 10–15 minutes to ensure stability.
     • If the error exceeds the allowable range, input correction values through the instrument’s built-in calibration menu and conduct a retest for verification after correction.
   • Applicable Scenarios: Industrial scenarios requiring high temperature precision, such as electronic SMT reflow soldering, medical sterilization, and material sintering.
2. Blackbody Radiation Source Calibration Method (Exclusive for High-temperature Infrared Testers)
   • Core Principle: A blackbody radiation source can simulate the thermal radiation characteristics of an ideal blackbody. It is suitable for non-contact infrared oven temperature testers (typically with a range above 600℃) and performs calibration based on the radiation thermometry principle.
   • Key Operational Points:
     • Set the emissivity of the blackbody radiation source to 1.0 (ideal blackbody state). Align the tester’s lens vertically with the radiation aperture at a distance specified in the instruction manual (usually 30–50 cm).
     • Set multiple high-temperature calibration points (e.g., 800℃, 1200℃, 1600℃). After the temperature stabilizes, compare the temperature displayed by the blackbody with the reading of the tester.
     • If the tester is used to measure specific materials (e.g., metals, ceramics), compensation calibration should be performed according to the emissivity of the corresponding material.
   • Applicable Scenarios: High-temperature non-contact temperature measurement scenarios such as metallurgical smelting, ceramic firing, and glass processing.

II. On-site Convenient Calibration (Suitable for Precision Verification Before Daily Production)

1. Standard Substance Melting Point Calibration Method (Low-cost and Easy to Operate)
   • Core Principle: The fixed and invariable melting point of a pure substance is used as a temporary temperature reference. During the melting process of the substance, the temperature remains constant, enabling rapid verification of the tester’s precision.
   • Common Standard Substances and Their Melting Points:

     Standard Substance	Melting Point (℃)	Applicable Scenarios
     Distilled Water Ice	0.0	Low-temperature calibration verification
     Analytical Grade Naphthalene	80.1	Medium-low temperature scenarios
     Pure Tin Block	231.9	Daily verification in the electronic soldering industry
     Pure Lead Block	327.5	Medium-high temperature scenarios (note protective measures)

   • Key Operational Points: Attach the sensor closely to the standard substance, heat it slowly until the substance melts, record the tester’s reading, and compare it with the theoretical melting point. A deviation of ≤±1℃ indicates qualification.
2. Homogeneous Equipment Comparison Calibration Method (Rapid Verification on Production Lines)
   • Core Principle: Use a qualified oven temperature tester that has passed laboratory calibration as a "standard reference". Bind its sensor with that of the tester to be calibrated at the same location and perform synchronous testing in the actual oven.
   • Key Operational Points:
     • Fix the sensors of the two instruments at the same temperature measurement point inside the oven (e.g., the center of the reflow soldering furnace conveyor belt, avoiding the furnace wall or air vents).
     • Operate the oven according to the normal production process and compare the temperature curves of the two instruments (heating rate, peak temperature, constant temperature duration).
     • If the deviation of key temperature points is ≤±1℃, the tester to be calibrated can be put into use normally.

III. Key Calibration Notes

1. Prioritize Sensor Calibration: Over 80% of the errors in oven temperature testers originate from sensors (e.g., thermocouple aging, thermal resistance oxidation). Before calibration, inspect the sensor appearance and cable continuity.
2. Control Calibration Environment: All equipment must be left to stand at room temperature (20℃±5℃) for more than 30 minutes before calibration to avoid initial errors caused by temperature differences.
3. Ensure Traceable Records: Generate a calibration report after each calibration, recording the model of the calibration equipment, calibration point data, error values, operator information, and date to meet the audit requirements of ISO and other systems.