Essential Test Devices: Don’t Leave Home Without Them

1. Replace the original fuse with a cheap one. Make sure to change your DMM fuse with an authorized fuse.

2. Use a bit of wire to get around the fuse. This might be the only thing between you and a voltage spike headed your way.

3. Use the wrong test tool for the job. Make sure the test tool holds the correct CAT rating.

4. Grab the cheapest DMM on the rack.Look for independent laboratory testing.

5. Leave your safety glasses in your shirt pocket. Put them on.

6. Work on a live circuit. De-energize the circuit whenever possible.

7. Fail to use proper lockout/tag-out procedures.

8. Keep both hands on the test. An old favorite of mine that I ignored one time when younger and it almost cost me my life. Don’t do it.

9. Neglect your test leads. Make sure they match CAT level of the job.

10. Hang on to an old test tool forever. New testers have new features and are worth the upgrade. Cheaper than an emergency room visit.

You may have noticed considerable mention about CAT levels. These levels are established in NFPA 70E. CAT 1 is for electronic systems (<240V); CAT 2 is for electrical panels, motors (240-600V); CAT 3 is for high-voltage areas such as utility transformers (1,600 amps). You will see these CAT markings on newer DMMs and other similar test devices (see photo).

(“Tech Talk” DMM Tip: Want to know a simple way to test if the fuse in your DMM is good? Place the DMM on the lowest resistance setting, then remove the black COM probe and make a loop by inserting the red + probe into the black DMM plug (COM -). You will basically get a short resistance reading (0.3 ohms) if the fuse is good, and high, open or over-range resistance reading if the fuse is blown. It’s a simple but effective test.)

Now let’s take a moment to look at some handy handheld test devices and products for today’s diversified technician:

TVR10/100/1000 LAN Tester (American Technical Publishers) is a good training book that covers many DMM fundamentals and troubleshooting techniques. The book also provides exposure to the many testing variations and DMM accessories.

The CH3 extended clamp head for Phoenix clamp-on meters (UEi) has a unique, patented slim clamp head design that makes it easy to clamp onto wires in a bundle and to go places normal clamp-ons cannot go.

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About the Author


Bob is currently a Security Sales & Integration "Tech Talk" columnist and a contributing technical writer. Bob installed his first DIY home intercom system at the age of 13, and formally started his technology career as a Navy communication electronics technician during the Vietnam War. He then attended the Milwaukee School of Engineering and went on to complete a Security Management program at Milwaukee Area Technical College. Since 1976, Bob has served in a variety of technical, training and project management positions with organizations such ADT, Rollins, National Guardian, Lockheed Martin, American Alarm Supply, Sonitrol and Ingersoll Rand. Early in his career, Bob started and operated his own alarm dealership. He has also served as treasurer of the Wisconsin Burglar and Fire Alarm Association and on Security Industry Association (SIA) standards committees. Bob also provides media and training consulting to the security industry.

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