Larry Eccleston has seen it all. For example, multimeters with a piece of wire wedged under the fuse to disable its safety features, or meters "that just exploded" whose interiors, it turns out, were filled with water. Burned-out hulks of machines asked to do more than they were ever designed to handle.
Eccleston, engineer manager of product evaluation for Fluke Corporation, does more than personally examine every digital multimeter that arrives in his test lab after an accident. He takes every chance he can get to remind those who work with electricity that safety measures aren't a pain in the neck -- they're the best route to reaching retirement.
The hazards of working with electricity aren't new, of course. But today they are probably more erratic -- and severe. As electronic and electrical systems become more complex and as the world increasingly becomes connected through the river of electricity that courses from one application to another, the dangers of measuring its flow have increased.
"That's why the real focus is in putting the effort in up front so an accident doesn't happen," Eccleston says.
If you're well prepared, with proper safety equipment and procedures and tools rated for the job you're performing, even if you wander into dangerous territory, your digital multimeter test tool can help handle an unexpected situation. Electrical dangers often carry no warning. "A good meter could have saved your life and you would never know it," Eccleston says.
It's not unheard of for an electrician, for example, to find himself the victim of a transient power spike that knocks him flat before he knows it's coming, thanks to a big motor kicking on or off somewhere upline. Occasionally a worker may end up working with lines holding significantly more juice than he realizes. It's also not unheard of for someone to work on a 12,000-volt line thinking he's on a 480 line.
That's why several years ago Fluke beefed up the safety net designed into each of its measurement tools and why today Fluke employs an expert like Eccleston to make sure safety comes first, from product concept to post-sale support. Whether it is the specially designed sand fuses or the rigorous testing to ensure component spacing meets or exceeds IEC standards, no detail is too small when it comes to meeting the new safety regulations.
The benefits are worth the hassle. Whether caught by a silent transient spike or stumbling into a sudden arc blast, operators a split-second away from an electrical accident are going to want test tools and safety equipment capable of defusing the emergency.
The first step is made at the time you purchase a test tool. You need tools that have been independently tested to verify they meet today's safety standards. Too many say they do but fail independent tests.
"Generally a $10 meter doesn't do the trick," Eccleston says. "Are severe burns on your hands and face worth $10? Some guys like the idea of disposable meters. They say, 'If one goes bad, I just throw it away.' But factor in the cost of replacing cheap meters along with the cost of the time it takes to go get a new one, the cost of potential serious injury or damage to a facility, and the cost of a cheap tool becomes very expensive."
Selecting the correct test tool for each job comes next. Those who would like to remain injury-free will do well to familiarize themselves with a bit of rule making known as IEC 1010.
Ranging from Category I protected low energy circuits to Category IV installations with high-powered lines exposed to outdoor environments, the rigorous IEC international standards are designed to keep you safe. Meters designed to the new standards are more capable of withstanding the hazards caused by transients and other dangers in today's electrical systems.
That's why before you start each job, it's important to take a minute and check the category rating and certification label of your test tools. It's not just a good work practice. It could save your life.
Look on the front of your meter. It should carry a designation of its CAT over voltage rating. Always make sure your measurement tool category rating matches how you're using it, even if that means switching from meter to meter throughout the day.
"The bottom line is, you have to match the meter to the application," Eccleston says. One meter, whether DMM, ScopeMeter, or clamp meter, doesn't fit all.
Category I -- typically covers electronic equipment
- Protected electronic equipment
- Equipment connected to (source) circuits in which measures are taken to limit transient over voltages to an appropriately low level
- Any high-voltage-low-energy source derived from a high-winding resistance transformer, such as the high-voltage section of a copier.
Category II -- single-phase receptacle connected loads
- Appliance, portable tools, and other household and similar loads
- Outlet and long branch circuits
- Outlets at more than 10 meters from CATIII source
- Outlets at more than 20 meters from CATIV source
Category III -- three-phase distribution, including single-phase commercial lighting
- Equipment in fixed installations, such as switchgear and polyphase motors
- Bus and feeders in industrial plants
- Feeders and short branch circuits, distribution panel devices
- Lighting systems in larger buildings
- Appliance outlets with short connections to the service entrance.
Category IV -- three-phase at utility connection, any outdoor conductors
- "Origin of installations," such as where low-voltage connection is made to utility power
- Electricity meters, primary overcurrent protection equipment
- Outside and service entrance, service drop from pole to building, run between meter and panel
- Overhead line to detached building, underground line to well pump.
"The main question is, are you using the right tool for your application," Eccleston says. "In milliseconds, an enormous amount of damage can be done."
Category II conditions are most prevalent, but that shouldn't lull those testing electricity lines and sources into complacency. As soon as you move from inside a house or garage outside or into an industrial setting, chances are you're dealing with Category III or Category IV. As soon as you get into large industrial motors, you're in Category IV territory.
"Category IV is very unforgiving," Eccleston warns. "Extra precautions should always be taken when dealing with Category IV."
Click here for 10 Dumb Things Smart People Do When Testing Electricity.
