While anyone who works with electricity quickly develops a healthy respect for anything that could possibly be live, even the best of us can make uncharacteristic mistakes when pushed for time. The following is a quick list of WHAT NOT TO DO when taking electrical measurements.


1. Replace the original fuse with a cheaper one. Digital multimeters (DMMs) that meet today’s safety standards include a special high-energy fuse designed to pop before an overload hits your hand. Fluke meters use a special sand-filled fuse designed to extinguish an arc within the fuse enclosure. Be sure to replace it with the same kind of authorized fuse. 

2. Use a bit of wire or metal to get around the fuse. That may seem like a quick fix if you’re caught without an extra fuse, but it won’t provide protection against a spike headed your way.

3. Use the wrong test tool for the job. Make sure your test tool holds the correct CAT rating for each job you do, even if it means switching DMMs throughout the day. (See Table 1)

4.  Grab the cheapest DMM on the rack. If that cheap test tool doesn’t actually have the safety features it advertised, you could end up a victim of a safety accident. Look for independent laboratory testing markings like CSA or UL that ensure the tool meets standards.

5.  Skip out on PPE. They’re called “safety” glasses for a reason. Take them out and put them on. The same goes for insulated tools, insulated gloves, ear plugs, your face shield/hood and arcresistant clothing.

6. Work on a live circuit. De-energize the circuit whenever possible, and verify it’s de-energized before starting work. If you have to work on a live circuit, make sure an arc flash risk assessment has been completed, use the NFPA 70E table H.3(b) to select the appropriate PPE, and verify the operation of your test tool by testing a known voltage source first.

7. Fail to follow lockout/tagout procedures. Lockout/tagout procedures exist to protect you from potentially fatal electric shock—don’t risk someone re-energizing your work environment.

8Multi-task while measuring. When working with live circuits, try not to hold the meter in one hand while testing with the other—in a transient situation, that could create a path toground through your heart. Hang or rest the meter or use a wireless read-out to get the meter out of your hands and the readings at eye level, and use an alligator clip for your ground, so that that you’re only using one hand to probe the energized conductor.

9. Neglect test leads. Test leads are a critical component of DMM safety. Make sure your leads match the CAT level of your job. Look for test leads with double insulation, shrouded input connectors, and test probes with finger guards and a non-slip surface. Test the leads with a known voltage before using. Consider leads with adjustable shrouds. There are even probes with built in fuses!

10. Hang onto an old test tool forever. Today’s test tools contain safety features unheard of even a few years ago. These features are worth the cost of an equipment upgrade and a lot less expensive than an emergency room visit. For example new standards restrict the length of metal in the tip of a test probe to 4mm or less in CATIII/IV environments.

Table 1. Measurement Categories IAW IEC/EN 61010-031
Table 1. Measurement Categories IAW IEC/EN 61010-031

MSC can help you create a safer workplace to keep your team protected from electrical hazards. For a free assessment, training, programs and products to stay safe, visit

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My Boss wanted me to put a FLUKE on wires that were at 750 volts. The machine was pulling 1000 amps. I told him that I would not do that. He told me ---- you and took the FLUKE from me and said that he would test it himself. I told him not to test the wires it was not safe. He put the FLUKE on the wires and at that moment tha amps droped to zero the field colapesed and a basket ball size of white fire came out of the FLUKE. He did not move right away and when he did he threw the FLUKE in the trash like it was the FLUKES falt. His hand was numb but other than that the boss was ok. It was a wonder he was not killed. He needed better training!


Could someone describe what the problem was in this scenario?

Was the meter not rated for 750V?

Were the leads not rated for 750V?

Did he literally, physically, place the meter ON the energized wires and the suddenly-collapsed field induced a back-EMF voltage in the meter that exceeded its rating?

Something else I'm not seeing??


A collapsing field from an inductive load.  I assume he was testing a motor or other such device.  When your car needs 4KV for the spark plugs, it does just that.  Charges and inductive load and then collapses it, thus the high voltage at the spark plug.  Now your Fluke meter is probably not rated for 4Kv plus...



Spot on. Use arc flash training and equipment as prescribed. Fluke testers for job needed are prerequisite for activity.


I  had a helper check a high voltage when the Fluke was set on amps. He got burned pretty bad and sued the company we were working for and they settled to keep from having to go to court. I think he got like $50,000. Idiots everywhere!!!


How much training did the apprentice have? I would always discuss the procedure and meter settings. I would check prior to my helper checking Voltage. Untill I was comfortable knowing the Apprentice was up to speed.


    Why is it, and what does it take, for very intelligent, trained, skilled people to do such stupid things.  I walked by a turning center where a maintenance tech was changing out the drive motor.  I noticed the enunciator lights were shinning bright so I asked him if the power was off.  He said, yeah, I relieved J... and he said it was off.  Did YOU check?  I told you J... said it was off.  Check anyway!  He pulled out his meter and...said...Oh, S.....   I probably saved his life that day but only by the grace of God because I happened to be walking by.  Always double check, always!


Glad no one was hurt and thanks for sharing Thomas.


NEVER take someone else's  word! Always verify yourself! When possible i will ground the circuit so im not just relying on my meter.


One of my safety talks has always been "check it HOT, check it NOT" I was working in the overhead on a monorail system and I checked a contactor that I knew was hot and my meter showed no voltage. I then got off the ladder and set to ohms touched the leads and read open, changed leads and found bad test lead. Later found out someone had used my meter, droped it and kept it from bouncing because he still had the probes in his hands. Allways check!!


I remember when Fluke was made in the U S A. Now it's junk.


An electrician was working on a machine but didn't have his meter with him. An engineed was near by and the electrician borrowed his meter (it was a Fluke) to check some fuses. He gave the meter back and a few minutes later the engineer made a voltage test and the meter blew up in his hands. The engineer did not check but the electrician gave the meter back and it was still set on ohms. Meters made today are more forgiving of this mistake but you should always double check your meter to make sure of the settings and that the leads are pulgged in to the proper place for what you are doing. You don't have to make a mistake to have something blow up in your face. You could just be in the wrong place at the wrong time. Wear your PPE. 


Thanks for sharing Dan. We couldn't agree more about the staying safe in the workplace by wearing the required PPE. 


A test meter is only as good as the person that is using it

Before each use the meter should be inspected and test for correct operation

1. Battery - The battery should be checked to assure adequate voltage

2. Test Leads - Should be inspected for insulation failures, broken leads, failed test tips, oil and grease contamination 

3. Meter Case - inspect for cracks, and other damage

4. Operation - Before using to determine the presence of voltage, test on a known live circuit, test the circuit to be worked on  and test again in the know live circuit again

Meters are their for our safety, taking care of your meter and other PPE is critical to each individual’s safety

Remember NFPA 70E states that any voltage over 50volts is to be considered high voltage


Thank you for the refresher course.


ALWAYS allow your meter to reach room temp if left in a service vehicle or other cold location. A service tech was severely injured by an arc blast while attempting to verify power on a 480 volt service. The meter had been out overnight in the truck at temperatures well below zero. It was determined coming into the warmer work location caused a light condensation to form in and on the meter. Lack of proper PPE contributed to the extent of injury.


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Fluke Corporation is the world leader in the manufacture, distribution and service of electronic test tools and software. Founded in 1948, Fluke products empower the manufacturing and service industries with critical testing and troubleshooting capabilities. Fluke has been a trusted test tool partner, helping you and your team work safely with tools that meet or exceed the safety standards of the demanding environments you work in. Get the solutions you need to keep your world up and running with Fluke tools from MSC.

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