It’s Not Just the Volts
By Davide Castelvecchi
The National Electrical Safety Awareness Month banner at SLAC’s main
entrance should serve as a reminder on the risks of making electrical
Using the wrong kind of multimeter can result in electric shock or, in
the case or voltage surges, in a flare that can cause fire, injury,
burns, permanent blindness, or death.
Accidents are more likely to happen if a multimeter is old, broken,
damaged or in bad condition, says SLAC Electrical Safety Engineer George
Burgueno (ESH). “Be sure the leads and probes are intact and clean,” he
Even a brand-new test tool can pose a hazard if improperly used. The
correct voltage rating alone does not offer sufficient protection
against voltage spikes.
Meters are rated according to the safety standards of the International
Electrotechnical Commission (IEC). The new IEC-1010-1 standard has
replaced the older IEC 348 and offers a significantly higher level of
safety, Burgueno says.
Under IEC-1010-1, meters are rated based on voltage and category. The
category can be I, II, III or IV. Higher-category meters can withstand
the voltage spikes that can occur at or near high-energy power lines,
regardless of their nominal voltage.
All meters used at SLAC must have an IEC-1010-1 category III or higher
rating. “Make sure that any meters that don’t have at least a IEC-1010-1
category III rating not be used,” Burgueno says.
All outdoor lines or high-energy equipment require the use of category
Burgueno reminds us that it is always safer to de-energize electrical
equipment and apply lock and tag than it is to work on energized
Furthermore, those who work on energized equipment (Hot Work) must have
written authorization and use the appropriate personal protective
Any questions on electrical safety can be addressed to Burgueno (Ext.
2039) or ESC chair Perry Anthony (Ext. 4354).
All multimeter users should read Fluke’s ABCs of Multimeter Safety, a
great source of safety tips available on-line at: