Velleman DCM270 Instrukcja Obsługi Pobierz pdf (Strona 2)

Information sheet

Velleman

2/3 Last update: 31/03/2010

2. Overvoltage/installation categories

DVMs are categorized depending on the risk and severity of transient overvoltage that

might occur at the point of test. Transients are short-lived burst of energy induced in

a system, e.g. caused by lightning strike on a power line.

On high-energy circuits this leads to hazardous situations as these circuits might

provide enough current to feed an arc-over resulting in a plasma breakdown or even

explosion.

Higher CAT-identification refers to electrical environments with higher power and

possibly higher energy transients.

A CAT I-rated meter

is suitable for

measurements on

protected electronic

circuits that are not

directly connected to

mains power, e.g.

electronics circuits,

control signals…

A CAT II-rated meter

is suitable for

measurements in

CAT I-environments

and mono-phase

appliances that are

connected to the

mains by means of a

plug and circuits in a

normal domestic

environment,

provided that the

circuit is at least

10m apart from a

CAT III- or 20m

apart from a CAT IV-

environment. E.g.

household

appliances, portable

tools…

A CAT III-rated

meter is suitable for

measurements in

CAT I- and CAT II-

environments, as

well as for

measurements on

(fixed) mono- or

poly-phased

appliances which are

at least 10m apart

from of a CAT IV-

environment, and for

measurements in or

on distribution level

equipment (fuse

boxes, lighting

circuits, electric

ovens).

A CAT IV-rated

meter is suitable for

measuring in CAT I-,

CAT II- and CAT III-

environments as well

as on the primary

supply level.

Note that for all

measurements on

equipment for which

the supply cables

run outdoors (either

overhead or

underground) a CAT

IV meter must be

used.

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Information sheet 2

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