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9
Select the right test tool:
• Choose a test tool rated to the highest
category and voltage for which it could
possibly be used (most often 600 or 1000
volt CAT III and/or 600 volt CAT IV).
• Look for the category and voltage marking
near the recessed input connectors of your
test tool and a “double insulated” symbol
on the back.
• Verify your test tool has been tested and
certified by two or more independent
testing laboratories, such as UL in the
United States and VDE or TüV in Europe by
looking for the symbols of these agencies
on (the back of) your test tool.
• Make sure that the test tool is made of
a high-quality, durable non-conductive
material.
• Check the manual to verify that the
ohms, continuity and capacitance circuits
are protected to the same level as the
voltage test circuit, to reduce hazards
when the test tool is used incorrectly in
ohms, continuity or capacitance mode (if
applicable).
• Verify that the test tool has internal
protection to prevent instrument damage
when voltage is incorrectly applied to
an amperage measurement function (if
applicable).
• Make sure that the amperage and
voltage of your test tool’s fuses meets
specifications. Fuse voltage must be as high
or higher than the test tool’s voltage rating.
• Be sure to use test leads that have:
- Shrouded connectors
- Finger guards and a non-slip surface
- Category ratings that equal or exceed
those of the test tool
- Double insulation (look for the symbol)
- A minimum of exposed metal on the
probe tips
Safety is everyone’s responsibility but
ultimately it is in your hands.
No tool by itself can guarantee your safety
when working with electricity. It’s the
combination of the right tools and safe
work practices that gives you maximum
protection. Here are a few tips to help you
in your work:
Make sure you always comply with (local)
regulations.
Work on de-energized circuits whenever
possible.
Use proper lock-out/tag-out procedures. If these
procedures are not in place or enforced, assume
that the circuit is live.
Use protective gear when working on live
circuits:
• Use insulated tools
• Wear safety glasses or a face shield
• Wear insulated gloves, remove watches or
jewelry
• Stand on an insulated mat
• Wear flame resistant clothing, not ordinary
work clothes
Inspect and test your test tool:
• Check for a broken case, worn test leads or
a faded display.
• Make sure the batteries still deliver
sufficient power to get reliable readings.
Many test tools have a low battery indicator
on the display.
• Check the test leads resistance for internal
breaks while moving the leads around
(good leads measure 0.1-0.3 Ohm).
• Use the meter’s own test capability to
ensure that the fuses are in place and
working right (see manual for details).
Apply the appropriate working
practices when measuring on live
circuits:
• Hook on the ground clip first, then make
contact with the hot lead. Remove the hot
lead first, the ground lead last.
• Use the three-point test method, especially
when checking to see if a circuit is dead.
First test a known live circuit. Second,
test the target circuit. Third, test the live
circuit again. This verifies that your test
tool worked properly before and after the
measurement.
• Hang or rest the test tool if possible.
Try to avoid holding it in your hands, to
minimize personal exposure to the effects
of transients.
• Use the old electrician’s trick of keeping
one hand in your pocket. This lessens the
change of a closed circuit across your chest
and through your heart.
Fluke: Where safety is built in
Overvoltage
Installation
Category
Working Voltage
(DC or AC RMS
to ground)
Peak Impulse
Transient
(20 repetitions)
Test Source
(Ω = V/A)
CAT I
600 V
2500 V
30 Ohm source
CAT I
1000 V
4000 V
30 Ohm source
CAT II
600 V
4000 V
12 Ohm source
CAT II
1000 V
6000 V
12 Ohm source
CAT III
600 V
6000 V
2 Ohm source
CAT III
1000 V
8000 V
2 Ohm source
CAT IV
600 V
8000 V
2 Ohm source
Table 2
Use meters with these markings:
1000 V CAT III or 600 V CAT IV
Transient test values for overvoltage installation categories.
(50 V/150 V/300 V values not included)
Use protective equipment such as safety glasses and
insulated gloves