I. Preparations Before Calibration
1. Environmental Requirements
Temperature: 20±2℃, fluctuation not exceeding 1℃ within 1 hour
Humidity: 45%~60%RH
Avoid airflow, vibration, and electromagnetic interference. A vibration damping table is recommended.
2. Equipment Status Check
Preheating: Analytical balances require ≥4 hours preheating; precision balances require ≥1 hour preheating; high-precision models (e.g., 0.01 mg) are recommended to preheat for 2-3 hours.
Leveling: Adjust the leveling bolts to center the bubble in the level indicator; the error should not exceed 0.2°.
Cleaning the Weighing Pan: Wipe the weighing pan and support with anhydrous ethanol to prevent residue from affecting weighing.
3. Standard Weight Selection
The weight grade should be at least one grade higher than the balance's accuracy. For example: A 0.01 mg balance requires E2 grade weights; a 1 mg balance can use F1 grade weights. Weights
Common specifications: 1g, 2g, 5g, 10g, 20g, 50g, 100g, 200g, etc.
II. Calibration Operation Procedure
1. Internal Calibration (Applicable to models with built-in weights)
Ensure the weighing pan is empty, press the "TARE" key to zero.
Press the "CAL" key to enter "CALINT" mode.
Press "Enter" to start calibration; the balance will automatically complete zero-point and range calibration.
The screen will display "Cal Done" or indicate zero, indicating calibration is complete.
✅ Advantages: Simple operation, no manual intervention required, suitable for quick daily calibration.
2. External Calibration (Manual Calibration, Highly Versatile)
Empty the weighing pan and press the "TARE" button to zero.
Press the "CAL" button; the screen will display the required weight value (e.g., "200g").
Use non-magnetic tweezers to gently place the standard weight in the center of the weighing pan and close the windproof door.
Wait for the value to stabilize; the balance will automatically complete the calibration.
Remove the weight; the screen will display "CAL END" or zero, indicating successful calibration.
⚠️ Note: Do not touch the weight directly with your hands to prevent sweat and grease from affecting its quality.
III. Verification and Recording After Calibration
1. Repeatability Test
Use the calibrated balance to perform 6–10 repeated weighings and calculate the Relative Standard Deviation (RSD):
RSD ≤ 0.1%: High precision, qualified
RSD > 0.3%: Recalibration or equipment status check required.
2. Data Recording
It is recommended to record the following information for traceability and auditing:
Calibration date, operator
Weight used: weight class and serial number
Zero drift value before and after calibration
3. Ambient temperature and humidity
✅ Tip: In GMP, pharmaceutical, and other compliant scenarios, it is recommended to have mandatory verification conducted by a legal metrology institution every 6 months to ensure data traceability.
