Checkweigher calibration, verification and validation
The three terms answer different questions. A dependable quality plan defines each activity, its evidence and the response to failure.
Calibration compares the weighing indication with traceable reference standards and records any deviation. Verification confirms that the system still performs within defined limits. Validation demonstrates that the complete process—including product handling, classification, tracking, rejection and records—is fit for its intended use.
Calibration: establish measurement relationship
Calibration uses suitable reference standards and a documented procedure to compare indicated and reference values. It does not automatically adjust the machine, and a calibration certificate alone does not prove that an unstable pack will be weighed or rejected correctly at line speed.
Verification: confirm the system remains in control
Routine checks can use controlled packs or reference weights to confirm correct classification and response. The procedure should define test points, frequency, operator, sequence, acceptance limits, records and action when a check fails. The interval should reflect risk, usage, environment and quality-system requirements.
Validation: prove intended use
Validation considers the whole application. It should challenge representative product formats, speeds, limit zones, reject tracking, reject confirmation, alarms, recipes, access levels and data. Regulated environments may also require controlled protocols, approvals and change management.
Build a traceable test record
Record machine identity, software or recipe version where relevant, reference equipment, product, speed, conditions, results, deviations and authorisation. Clear evidence makes trends visible and helps distinguish weighing drift from product-handling or process changes.
Plan the response to a failed check
Define how production is contained, the last known-good check is identified, affected product is assessed, the cause is investigated and the system is returned to service. This decision path is as important as the test itself.
Keep reference standards controlled
Select standards appropriate to the required test, identify them clearly, protect them from damage or contamination and maintain traceability in line with the site’s quality system. The chosen reference method must be capable enough for the decision being made.
Specification checklist
- Named test and purpose
- Machine and recipe identification
- Controlled reference standards
- Defined product, speed and conditions
- Acceptance limits
- Reject and alarm challenges
- Recorded result and authorisation
- Documented failure response
Answers for project teams
Does calibration prove reject performance?
No. Calibration addresses weighing indication. Reject timing, tracking, confirmation and containment need functional verification or validation.
How often should a checkweigher be verified?
Use a documented, risk-based interval considering product risk, process stability, usage, environment, customer requirements and previous results.
Is a test weight enough for a dynamic checkweigher?
A reference weight is useful for measurement checks, but representative moving products are also needed to challenge handling and the complete line response.
Related checkweighing guidance
Turn the requirement into a practical specification.
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