Test & Measurement

Tip of the Week: Take Proper Care of Your Test and Measurement Equipment

June 20, 2016

Replacing a digital multimeter is costly, so avoid uses that are likely to damage it.

Unless your employer provides your test equipment, you’ve probably made a significant investment in at least one good digital multimeter (DMM). Maybe two. And you’d like to avoid that outlay again for a while. So would your employer, if your DMM is employer-provided. And if you’d like to improve your test equipment arsenal, replacing is going to deplete funds that could have been spent on acquiring more testing capability.

To avoid damaging a DMM, steer clear of these mistakes:

• Using the wrong jacks. At a nuclear power plant, an electrician turned his DMM into a molten mass. He accomplished this job-ending feat by measuring from a 480V bus to ground while having his test leads plugged into the current jacks. That 2A fuse isn’t designed to protect against this sort of abuse.

• Using the wrong setting. Most meters have some protection against this. For example, you have the DMM set on the 20VDC scale, but are measuring 120VAC. This typically will not harm the meter, you’ll just see “OL” on the screen. But try this stunt when the meter is providing power from its battery to the resistance terminals and you could seriously damage the meter.

• Storing it for “immediate access” rather than keeping it in a meter case. Most DMM cases have a pouch for the test leads, and you should use that. Wrapping the test leads around the meter and tossing it into a gang box (or shoving it into a tool pouch) is a sure way to degrade the integrity of those leads. If someone borrows your meter and returns it with the leads wrapped around it, replace the leads before using the meter.

• Using the wrong meter. If your meter is rated CATIII, don’t use it at the service switchgear. If it’s rated up to 1,000V, don’t even get it out around medium-voltage equipment.

• Using the current jacks. This isn’t in itself a problem, but if you’re in an industrial setting, it probably is. That’s because a typical DMM can measure small current values that are greatly exceeded by those you’d really care about in an industrial setting. Quick, how much current is that 100 HP motor drawing? Don’t use your DMM current jacks to try to read that. Instead, use a current clamp or other accessory. Typically, these will convert the current to a voltage you can read on the meter’s display as the amount of current. You can safely use the DMM’s current jacks, but be very aware of the application and environment before even considering doing so.

About the Author

Mark Lamendola

Mark is an expert in maintenance management, having racked up an impressive track record during his time working in the field. He also has extensive knowledge of, and practical expertise with, the National Electrical Code (NEC). Through his consulting business, he provides articles and training materials on electrical topics, specializing in making difficult subjects easy to understand and focusing on the practical aspects of electrical work.

Prior to starting his own business, Mark served as the Technical Editor on EC&M for six years, worked three years in nuclear maintenance, six years as a contract project engineer/project manager, three years as a systems engineer, and three years in plant maintenance management.

Mark earned an AAS degree from Rock Valley College, a BSEET from Columbia Pacific University, and an MBA from Lake Erie College. He’s also completed several related certifications over the years and even was formerly licensed as a Master Electrician. He is a Senior Member of the IEEE and past Chairman of the Kansas City Chapters of both the IEEE and the IEEE Computer Society. Mark also served as the program director for, a board member of, and webmaster of, the Midwest Chapter of the 7x24 Exchange. He has also held memberships with the following organizations: NETA, NFPA, International Association of Webmasters, and Institute of Certified Professional Managers.