Standard Operating Procedure (SOP)

Here’s a standard Standard Operating Procedure (SOP) for Calibration of Balance that can be customized based on your organization’s requirements and the specific balance model(s) used:

1. Objective

To ensure accurate and reliable measurements by calibrating the balance using certified weights, in compliance with applicable standards and guidelines.

2. Scope

This procedure applies to all analytical, precision, and top-loading balances used in [Lab/Production Area] at [Company Name].

3. Responsibilities

• Operator: Perform the calibration and record the data.

• Supervisor/QA: Review and verify the calibration data.

• Maintenance/Engineering (if applicable): Support in case of malfunction.

4. Definitions

• Calibration: The process of configuring the balance to provide a result for a sample within an acceptable range.

• Tare: Resetting the balance to zero after placing a container.

• Internal Calibration: Automatic calibration using internal weights.

• External Calibration: Calibration using external certified weights.

5. Materials and Equipment

• Balance to be calibrated

• Certified calibration weights (Class E2, F1, or as per requirement)

• Calibration logbook/form

• Clean brush or lint-free cloth

6. Procedure

6.1 General Precautions

• Ensure the balance is clean and on a vibration-free, level surface.

• Allow the balance to warm up for at least 30 minutes (if recently powered on).

• Avoid airflow or direct sunlight on the balance.

• Use gloves or tweezers to handle calibration weights.

6.2 Internal Calibration (if applicable)

1. Press the “Cal” or “Internal Calibration” button.

2. Allow the balance to complete the process.

3. Confirm calibration completed without errors.

4. Record the calibration in the logbook.

6.3 External Calibration

1. Press the “Cal” or “Ext Cal” button to start external calibration mode.

2. The display will prompt for a specific weight (e.g., 100g).

3. Place the certified weight when prompted.

4. Wait until the balance displays “OK” or returns to zero.

5. Repeat the process with other required weights (e.g., 1g, 10g, 500g, as needed).

6. Record the actual readings and compare them with the expected values.

7. Record the results in the calibration log.

8. If results are out of tolerance, tag the equipment as “Out of Service” and report to supervisor.

7. Acceptance Criteria

• The balance reading must not deviate from the actual weight by more than the specified tolerance (e.g., ±0.1 mg for analytical balance).

• Tolerance limits should be defined based on balance class and usage.

8. Frequency of Calibration

• Internal calibration: Daily or before each use (as applicable)

• External calibration: Monthly or as defined in the calibration schedule

• After relocation or maintenance

9. Documentation

• Calibration logbook

• Calibration certificate (for certified weights)

• Out-of-tolerance report (if applicable)

10. Abbreviations

• SOP – Standard Operating Procedure

• QA – Quality Assurance

• mg – milligram

• g – gram

11. References

• Manufacturer’s manual for the balance

• ISO/IEC 17025

• USP <41>, <1251>

• Internal Quality Manual.

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