I. Routine Periodic Calibration (Preventative)
High Usage Frequency: If the equipment is used more than 3 times per week, it is recommended to calibrate it every 6 months.
Routine Maintenance Cycle: Even with low usage frequency, it should be calibrated at least once a year to ensure long-term stability.
Before First Use of New Equipment: Newly purchased or repaired instruments must be calibrated to confirm the accuracy of factory parameters.
II. Performance Abnormal Signals (Fault-Related)
When the test results show the following abnormalities, it indicates that the equipment may be inaccurate and requires urgent calibration:
1. Large Fluctuations in Test Results
Multiple test results for the same sample differ by ≥0.5 grades (e.g., from grade 4 to grade 3.5), indicating unstable friction pressure, stroke, or speed.
2. Uneven or Misaligned Color Staining on the Rubbing Cloth
Wrong friction marks or uneven pressure may be due to deformation of the friction head, uneven sample stage, or malfunction of the loading system.
3. Significant Counter Error: The actual number of friction cycles deviates from the set value by more than ±1 cycle (e.g., set to 10 cycles, but actually completes 9 or 11 cycles).
4. Abnormal Friction Speed: The friction speed feels too fast or too slow; the measured speed deviates from the standard value (e.g., 60 cpm ± 2 cpm).
Stroke Length Variation: The measured stroke exceeds 100mm ± 1mm, affecting the consistency of the friction area.
III. After Environmental or Operational Changes:
After equipment movement or vibration: such as handling or dropping, internal structures may become loose.
After replacing key components: such as the friction head, loading spring, motor, etc.
Dramatic Changes in Ambient Temperature and Humidity: After long-term use in non-standard environments (not 20±2℃, 65±4%RH), it is recommended to recalibrate the equipment when returning to a standard environment.
IV. Standard Updates or Compliance Requirements
New Standard Implementation: For example, GB/T 3920-2024 will be implemented on January 1, 2027. Existing equipment must be calibrated in advance to ensure compliance with the new requirements.
Before Customer Factory Inspection or Audit: Exporting companies must provide a valid calibration report to prove the traceability of the testing data.
