CORE CONCEPTS
Products and revisions
A product is the device under investigation. A revision is a specific physical configuration of it: the board revision, and where relevant the firmware, enclosure, cables and operating mode used during the test.
Evidence belongs to the revision it was produced on. A new revision does not inherit earlier results. Where a later revision shares facts with an earlier one, the shared facts are recorded explicitly rather than assumed.
WHY IT MATTERS
A pass on Rev B says nothing about Rev C until someone establishes which differences between them could affect the result.
Requirements and applicability
A requirement is a rule, the version of that rule, and the basis for applying it to this product. For radiated emissions the basis typically includes the equipment class, the frequency range, the measurement distance and the detector the limit is defined for.
Applicability is recorded, not implied. If the basis for applying a requirement is unknown, for example the equipment class has not been stated, it is shown as missing and the check does not run.
Evidence and provenance
Evidence is a measurement together with its test conditions and a reference to where it came from. A value without its source is not used for evaluation.
| Field | Meaning |
|---|---|
| Frequency | Frequency of the recorded emission, in MHz |
| Level | Field strength as reported, in dBµV/m |
| Detector | Quasi-peak, peak or average |
| Distance | Antenna measurement distance, in metres |
| Polarization | Horizontal or vertical |
| Source | The document the value came from and its location, such as page or table |
Provenance is recorded at the level the source supports. A confirmed value keeps both its source reference and a record that it was confirmed.
Observations and hypotheses
Every item in an investigation carries one of four states. The states describe how something is known. They are not a verdict.
- Observed
- Recorded measurements and physical test results.
- Known
- Confirmed product facts with supporting sources.
- Inferred
- Candidate explanations requiring investigation.
- Missing
- Information needed before a check or decision can proceed.
Suggested tests, completed tests and confirmed causes
These three are kept separate throughout.
| Item | What it means | What it does not mean |
|---|---|---|
| Suggested test | A proposed next step, awaiting review | That anything has been measured |
| Completed test | A test that was run, with a recorded result and conditions | That the hypothesis it tested is true |
| Confirmed cause | An explanation an engineer has accepted on the basis of completed tests | That the fix holds on other revisions |
Reviews and historical decisions
A review records a decision, the evidence it relied on and the revision it concerns. Earlier decisions are preserved when new evidence arrives, so the reasoning behind a past next step can still be read.
A historical result stays attached to the revision it was measured on. It is not overwritten by a later retest on a different revision.
PRODUCT DIRECTION
Automatically returning affected evidence to review when a revision changes is part of where Crado is heading. It is not described here as current functionality. The illustrative concept on the homepage shows the intended behaviour.