A CAT marking states a measurement category and voltage claim; a product label alone does not independently verify that claim. Check the exact instrument and accessories, the applicable instructions, and supporting conformity documents or test reports. Teardown photographs can reveal construction details, but they cannot establish that a complete instrument has passed the relevant safety tests.
Category and voltage belong together
Measurement categories describe environments with different transient demands. The voltage rating is part of the claim. A category number without its accompanying voltage, terminals and permitted function is incomplete. A high maximum displayed voltage is also a different property from suitability for a particular measurement environment.
Fluke’s category explanation [1] provides an introduction, while HSE GS38 [2] addresses equipment used on UK low-voltage electrical systems. Neither source turns an unverified label on another manufacturer’s instrument into independent proof.
Build an evidence trail for the exact version
| Evidence | Record | Limit |
|---|---|---|
| Label and manual | Model, revision, terminals, category, voltage and restrictions | A manufacturer claim, not independent verification |
| Declaration of conformity | Issuer, model, standards, date and document origin | Do not describe self-declaration as third-party certification |
| Third-party report or certification | Issuing body, verifiable record, model, scope and accessories | A logo or unrelated report number is insufficient |
| Teardown | Original images, sample identity and visible protection components | Construction evidence, not a completed safety assessment |
| Calibration certificate | Instrument identity, measurements, uncertainty and conditions | Measurement performance, not CAT validation |
A document should be obtainable from a traceable issuer and match the product being supplied. If the relevant report cannot be verified, record “not independently verified”; do not turn missing evidence into a categorical finding of either safety or non-compliance.
What a teardown can—and cannot—show
Input fuses, protection resistors, PTCs, MOVs, clearances and slots may be visible in photographs. HKJ’s protection explanation [3] and Mark Hennessy’s safety discussion [4] help explain their roles. The presence of a recognisable component does not prove its rating, authenticity or performance in the assembled design.
A fuse marked for a particular current is not fully described by that current alone. Voltage, breaking capacity, dimensions and the manufacturer’s required replacement type also matter. This article is not an instruction to modify protection or substitute components.
Photographs may not expose every layer, material property or manufacturing variation. A review sample from an earlier year must not be assumed to establish the construction of current stock. Destructive or high-energy tests require appropriate facilities and competence; they are not a shortcut for a home review.
Include the leads and the task
The measurement system includes probes, leads, adaptors and their condition. Ratings and permitted configurations can change with accessories such as probe caps. Suitability must be checked for the actual combination and task, not just the highest marking on the meter.
GS38 is especially relevant to UK electrical work. A non-contact or single-pole indication must not be presented as proof that equipment is dead. Our UK source directory explains where to find the relevant professional guidance; this page supplies no isolation or live-testing procedure.
Meter & Probe has not certified any instrument or independently verified a product’s CAT rating. CE or UKCA marking alone is not third-party certification, and a calibration certificate does not change that distinction.
Sources & scope
Sources checked on 22 September 2026. Numbered references above point to the original publishers below. Their sample measurements are not Meter & Probe measurements; manufacturer material is identified separately.
- Fluke — IEC category ratings ↗Manufacturer explanation of measurement categories
- HSE — GS38: Electrical test equipment for use on low voltage electrical systems ↗UK regulator guidance
- HKJ — Multimeter input protection ↗Engineering explanation; not certification
- Mark Hennessy — Multimeter safety ↗Independent discussion of safety evidence
No product in this guide has been bench-tested or certified by this publication. Evidence policy · Corrections
Keep the conditions with the reading.
Use the blank CSV to record the instrument, range, reference, environment and result.
Download measurement record ↓