Velleman APPA106 ユーザーズマニュアル

 

Velleman

®

 

2/3 

       Last update: 31/03/2010 

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.