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Create Characteristics
Define new characteristics, assign tolerance ranges, and classify as Special Characteristics (SC) or Critical Characteristics (CC).
Link to Failure Modes
Connect characteristics to failure modes in Design FMEA (DFMEA) and establish traceability to risk controls.
Set Target Values & Tolerances
Define nominal values, upper and lower limits, and tolerance specifications for manufacturing validation.
Use Characteristics PowerSheet
Access the interactive Characteristics sheet for bulk viewing, editing, and FMEA cross-linking.
Why Characteristics Matter
Characteristics are critical in automotive functional safety workflows because they:- Enable Design-to-Manufacturing Traceability — Link design requirements through failure modes to control plans
- Support ISO 26262 DFMEA — Identify which design parameters affect fault detection and mitigation
- Classify Special Characteristics (SC) — Flag product attributes that impact functional safety per AIAG-VDA FMEA
- Integrate with FMEA Severity — Connect failure mode severity to characteristic tolerance exceedance
- Enable Control Plan Integration — Define what to measure, where, and with what acceptance limits
Workflow Overview
Key Concepts
Characteristics in the V-Model
Characteristics sit at the design level of the ISO 26262 V-Model. They represent measurable aspects of system elements (hardware, software, or manufacturing process) whose variation could trigger or mask a failure mode. Examples:- Hardware: Sensor sensitivity range, amplifier gain tolerance, connector pin geometry
- Software: Filter cutoff frequency, timing threshold, signal processing scale factor
- Manufacturing: Material hardness, coating thickness, weld penetration
Special Characteristics (SC) and Critical Characteristics (CC)
| Type | Definition | ISO 26262 Role | Control Requirement |
|---|---|---|---|
| SC | Design or process characteristic that affects functional safety | Part of DFMEA risk mitigation strategy | Mandatory production monitoring per control plan |
| CC | Business-critical characteristic (quality, cost, performance) | Not directly safety-related | Customer requirement or industry standard (e.g., IATF 16949) |
| Regular | Standard design parameter with tolerance spec | Contributes to product function | Standard manufacturing control |
Tolerance and Target Values
Each characteristic requires:- Nominal/Target Value — the design intent
- Upper Specification Limit (USL) — maximum acceptable value
- Lower Specification Limit (LSL) — minimum acceptable value
- Tolerance — USL − LSL (often expressed as ±tolerance around nominal)
- Sampling frequency — how often to measure
- Measurement method — gage, test equipment, visual inspection
- Reaction plan — what to do if out of spec
Getting Started
- Create Characteristics — Define a new characteristic with name, description, and initial classification
- Set Target Values and Tolerances — Add nominal, USL, and LSL values
- Link to Failure Modes — Connect to Design FMEA and specify how failure affects the characteristic
- Use Characteristics PowerSheet — Access the interactive sheet for bulk edits and FMEA cross-linking
Common Tasks
| Task | Guide | Time |
|---|---|---|
| Create a new characteristic from a design requirement | Create Characteristics | 5 min |
| Specify tolerance limits for a sensor characteristic | Set Target Values and Tolerances | 10 min |
| Link a design parameter to its failure modes in DFMEA | Link to Failure Modes | 15 min |
| Bulk-update characteristics and view FMEA traceability | Use Characteristics PowerSheet | 20 min |
| Classify a characteristic as SC due to safety impact | Create Characteristics (Step 4) | 2 min |
Related Pages
- Design Requirement — Parent work item type for characteristics
- Failure Mode — DFMEA failure modes linked to characteristics
- Control Plan Item — Downstream control strategy using characteristic targets
- Characteristics Sheet (PowerSheet Configuration) — Full technical reference
- AIAG-VDA FMEA Methodology — Framework for SC/CC classification
- Create Design FMEA Document — DFMEA workflow that uses characteristics
After defining characteristics, you’ll typically move into control planning to specify how to verify that characteristics meet their targets in production. See Control Plan Workflow for the full quality assurance flow.