Sub-topic #3: Evaluating an Analytical Balance

• The analytical balance should be regularly evaluated to determine whether it needs any on-site

  modification, repair, or calibration.
• Calibration – act of ensuring that the instrument will

  produce results which are accurate.
• Problems can occur due to defective components or

  because of how users operate them.
• Repeatability Measurement

  • Ensures that it delivers accurate results consistently for a given object.
• Repeatability Measurement

  • Procedure: Single sample is weighed multiple times, and the variation in the readings is analyzed.
• Repeatability Measurement

  • Low standard deviation = good repeatability
• Corner Load Testing

  • Ability to generate the same readings for an object, regardless of where it is placed on the weighing pan.
• Corner Load Testing

  • Procedure: Test weight is placed at various points on the balance plate, the readings are compared to check if they are consistent across all positions.
• Linearity Testing

  • Ensures that it delivers the same sensitivity throughout its functional range.
• Linearity Testing

  • Procedure: Place different known weights on the balance (spanning the balance’s capacity). The readings are compared to the true values.
• Linearity Testing

  • The difference between the actual weight and the measured value is analyzed.