Application Note

ABCs of multimeter safety Fluke Corporation 3
What does the
symbol indicate?
A product is marked CE
(Conformité Européenne)
to indicate its conformance to
certain essential requirements
concerning health, safety,
environment and consumer
protection established by
the European Commission
and mandated through the
use of “directives.” There are
directives affecting many
product types, and products
from outside the European
Union can not be imported and
sold there if they do not comply
with applicable directives.
Compliance with the directive
can be achieved by proving
conformance to a relevant
technical standard, such as
IEC 61010-1 for low-voltage
products. Manufacturers are
permitted to self-certify that
they have met the standards,
issue their own Declaration
of Conformity, and mark the
product “CE.” The CE mark is
not, therefore, a guarantee of
independent testing.
It’s not just the
voltage level
In Figure 1, a technician working
on office equipment in a CAT 0
location could actually encounter
dc voltages much higher than the
power line ac voltages measured
by the motor electrician in the CAT
III location. Yet transients in CAT 0
electronic circuitry, whatever the
voltage, are clearly a lesser threat,
because the energy available to
an arc is quite limited. This does
not mean that there is no electri-
cal hazard present in CAT 0 or CAT
II equipment. The primary hazard
is electric shock, not transients
and arc blast. Shocks, which will
be discussed later, can be every
bit as lethal as arc blast.
To cite another example, an
overhead line run from a house
to a detached workshed might be
only 120 V or 240 V, but it’s still
technically CAT IV. Why? Any
outdoor conductor is subject to
very high energy lightning-related
transients. Even conductors buried
underground are CAT IV, because
although they will not be directly
struck by lightning, a lightning
strike nearby can induce a tran-
sient because of the presence of
high electro-magnetic fields.
When it comes to Overvoltage
Installation Categories, the rules
of real estate apply: it’s location,
location, location...
(For more discussion of Installation
Categories, see page 6, “Applying cat-
egories to your work.”)
Independent testing is the
key to safety compliance
Look for a symbol and listing
number of an independent test-
ing lab such as UL, CSA, TÜV or
other recognized testing organi-
zation. Beware of wording such
as “Designed to meet specifica-
tion ...” Designer’s plans are
never a substitute for an actual
independent test.
How can you tell if you’re
getting a genuine CAT III or CAT
II meter? Unfortunately it’s not
always that easy. It is possible
for a manufacturer to self-
certify that its meter is CAT II or
CAT III without any independent
verification. The IEC develops
and proposes standards, but it
is not responsible for enforcing
the standards.
Look for the symbol and
listing number of an indepen-
dent testing lab such as UL,
CSA, TÜV or other recognized
approval agency. That symbol
can only be used if the product
successfully completed testing
to the agency’s standard, which
is based on national/interna-
tional standards. UL 61010-1,
for example, is based on IEC
61010-1. In an imperfect world,
that is the closest you can come
to ensuring that the multimeter
you choose was actually tested
for safety.
Independent testing
Tool Tip
Non-contact voltage detectors are a
quick, inexpensive way to check for
the presence of live voltage on ac
circuits, switches and outlets before
working on them.
1. Verify the voltage detector function is working properly.
2. Make sure the detector is rated for the level of voltage being
measured and is sensitive enough for your application.
3. Make sure that you also wear the appropriate PPE based on
the environment you're in.
3. Make sure you’re grounded (through your hand, to the floor),
to complete the capacitive voltage connection.
4. Make sure the hazardous voltage is not shielded.
Use only a digital multimeter or contact type voltage tester to
test for the absence of voltage.
This meter has a built-in non-contact voltage tester.