Learn how to verify the performance of hardness tester used to check the hardness of tablets. Step-by-step calibration using standard weights, tolerance limits, and QA documentation.
Tablet hardness testing is a critical quality control parameter in pharmaceutical manufacturing. Accurate calibration of the hardness tester ensures reliable measurement of tablet strength. This guide explains how to verify the performance of Hardness Tester used to check the hardness of tablets using standard weights and a force gauge.
🎯 Purpose of Calibration
The calibration of a hardness tester is performed to:
- Ensure accurate measurement of tablet hardness
- Maintain compliance with GMP and QA standards
- Detect deviations in force measurement
- Guarantee consistent product quality
⚙️ Calibration Principle
The hardness tester operates using a force gauge. Calibration is performed by applying standard weights and verifying that the displayed force matches the applied load.
🧾 Calibration Procedure
Step 1: Preparation
- Take out the force gauge to be calibrated
- Hold the force gauge vertically upward
- Adjust the pointer to zero position
Step 2: Calibration Using Standard Weights
- Apply 1 kg standard weight to the hook
- Observe and record the reading on the force gauge
- The reading should match 1 kg tension
- Reset the gauge to zero
Step 3: Repeat for Additional Weights
Perform the same procedure for the following weights:
- 1.0 kg
- 2.0 kg
- 5.0 kg
- 10.0 kg
- 20.0 kg
- 30.0 kg
📊 Acceptance Criteria (Tolerance Limits)
- Tolerance: ± 0.25 kg / ± 0.1 kg
The measured force should fall within the acceptable tolerance range for each applied weight.
📅 Calibration Frequency
- Perform calibration once every 6 months
- Maintain proper records for regulatory compliance
📝 Calibration Record Requirements
The calibration report should include:
- Instrument details (Make, Model, Instrument No.)
- Applied weights and corresponding readings
- Initial and final readings
- Difference calculation
- Final conclusion (Satisfactory / Not satisfactory)
- Signatures (Done by / Checked by)
- Next calibration due date
⚠️ Out-of-Calibration Handling
- If the instrument does not meet tolerance:
- Label it as “Out of Calibration”
- Send for repair or servicing
- After repair:
- Recalibrate before use
🔧 Maintenance Tips
- Keep the force gauge clean and properly stored
- Avoid dropping or mechanical shock
- Regularly inspect hooks and springs
- Follow manufacturer’s instructions
✅ Conclusion
Routine calibration ensures that tablet hardness measurements remain accurate and reliable. Following this SOP to verify the performance of Hardness Tester used to check the hardness of tablets helps maintain product quality, compliance, and data integrity in pharmaceutical manufacturing.
❓ Frequently Asked Questions (FAQs)
1. Why is hardness tester calibration important?
It ensures accurate measurement of tablet strength, which affects product quality and performance.
2. What is used for calibration of hardness testers?
Standard weights are used to calibrate the force gauge.
3. What is the acceptable tolerance limit?
The tolerance is typically ±0.25 kg or ±0.1 kg.
4. How often should calibration be performed?
Calibration should be done once every six months.
5. Why is the force gauge held vertically?
To ensure accurate force measurement without gravitational error.
6. What should be done if calibration fails?
Label the instrument as “Out of Calibration” and send it for servicing.
7. Is recalibration required after servicing?
Yes, recalibration is mandatory before reuse.
8. What weights are used during calibration?
1 kg, 2 kg, 5 kg, 10 kg, 20 kg, and 30 kg standard weights.
9. What does zero adjustment mean?
It ensures the gauge starts measurement from a true zero reference.
10. Can mechanical damage affect calibration?
Yes, damage to the spring or hook can lead to incorrect readings.