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Module 03 / Lesson 3.3 · Self-paced learning

Trace a requirement to a design decision

Write an evidence-linked DQ row that keeps later testing visible.

2.3 minutes · English captions · Illustrations and worked example

This lesson’s core explanations and worked-example reasoning are narrated. The table restates the example for reference; the practice activity and model answer are reading exercises.

English captions available.

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Narration and visual explanations

Open View Technical Explanation to see each diagram, its text description and the matching narration. Standard abbreviations and numerals are used visually.

Part 1 of 4

A measurable teaching assumption

View Technical Explanation · Diagram 1
A measurable teaching assumption — diagram 1. Description below.
R-03 is a fictional indication requirement at three reference points; its criterion does not cover every process-performance question. The left chart shows sensor, transmitter and display bounds of 0.2 °C each, with a 0.6 °C sum and a fictional 0.5 °C limit. Key points: R-03: indication accuracy; 20 / 40 / 60 °C points; ±0.5 °C example limit.

Lesson explanation

For a separate worked example, assume a fictional process owner has approved temperature indication at 20, 40 and 60 °C with error no greater than ±0.5 °C. These are teaching assumptions, not general GMP tolerances or real project approvals. Requirement R-03 concerns indication accuracy. It does not establish product temperature uniformity, mixing performance or an acceptable manufacturing process range.

Part 2 of 4

Compare the measurement chain

View Technical Explanation · Diagram 2
Compare the measurement chain — diagram 2. Description below.
Three component bounds add conservatively to ±0.6 °C; the chain does not yet support the ±0.5 °C teaching requirement. The left chart shows sensor, transmitter and display bounds of 0.2 °C each, with a 0.6 °C sum and a fictional 0.5 °C limit. Key points: Sensor: ±0.2 °C; Transmitter: ±0.2 °C; Display: ±0.2 °C.

Lesson explanation

The supplier lists three component error bounds of ±0.2 °C each: sensor, transmitter and display. If they can all act in the same direction, the simple worst-case sum is 0.6 °C. That exceeds the worked requirement of 0.5. Calling each component accurate would miss the chain. This conservative teaching calculation is not a complete uncertainty budget or an automatic rejection of every possible design. Other combination methods exist, but their assumptions, correlations and intended decision must be justified by appropriate metrology expertise.

Part 3 of 4

Write the traceability row

View Technical Explanation · Diagram 3
Write the traceability row — diagram 3. Description below.
One requirement links to specific design evidence, an unresolved gap and planned later verification; the row does not claim testing was performed. The left chart shows sensor, transmitter and display bounds of 0.2 °C each, with a 0.6 °C sum and a fictional 0.5 °C limit. Key points: Requirement and criterion; Design evidence reference; Gap and verification plan.

Lesson explanation

The row identifies R-03, the criterion, sensor schedule S-07 revision B and the calculation. Its decision is not demonstrated. The action is to propose a justified measurement-chain design or revise the requirement through authorized change, not quietly relax the criterion. Installation checks must confirm the selected components. Operational testing must challenge the assembled chain under the approved method. DQ plans this evidence; it does not invent its results.

Part 4 of 4

Close the row with evidence

View Technical Explanation · Diagram 4
Close the row with evidence — diagram 4. Description below.
A revised design can close the design gap only after review; later verification remains required even when design evidence is adequate. The left chart shows sensor, transmitter and display bounds of 0.2 °C each, with a 0.6 °C sum and a fictional 0.5 °C limit. Key points: Revised design received; Recalculate and review; Retain future verification.

Lesson explanation

Suppose the supplier proposes lower-error components. Review their applicable conditions and recalculate the chain; do not close the row merely because a new datasheet arrived. If the revised design supports the requirement, record the rationale and reviewer decision. Keep the later installation and operational checks in the verification plan. Distinguish design evidence adequate from installed performance demonstrated. The workbook contains a filled row and a blank row for practice.

Worked example

Fictional worked example — not an approved site record
FieldFilled teaching row
RequirementR-03: indication error within ±0.5 °C at 20, 40, 60 °C (fictional approved assumption)
EvidenceS-07 rev B; three applicable component bounds of ±0.2 °C
Design reviewWorst-case bound 0.6 °C; requirement not yet supported
ActionSupplier proposes suitable chain; metrology reviews applicability and decision rule
Later verificationIQ component identity; OQ assembled-chain challenge; results not yet available

Explore the conservative error bound

Positive component bounds in °C; sum assumes aligned errors. Fictional requirement 0.50 °C. This arithmetic is not a full uncertainty budget.

Worst-case sum: 0.60 °C. Exceeds the fictional 0.50 °C requirement.

Apply it · Activity 3

Complete one DQ traceability row for R-03. Explain why three ±0.2 °C components do not automatically meet a ±0.5 °C chain requirement.

Open workbook activity
Compare with model reasoning

Worst-case sum is 0.6 °C. Record the design gap, evidence reference and supplier action. Reassess revised components and retain installation/assembled-chain verification. Do not treat this sum as a full uncertainty budget.

Knowledge check

1. Three ±0.2 °C component bounds can align. Against ±0.5 °C, what does the conservative sum show?

Technical sources