Recap of Part 1
In Part 1 we covered some of the common errors when using digital multimeters (DMM) that can lead to serious injury, such as when the multimeter is placed in the incorrect setting or the leads are plugged into the wrong jack ports for a test the digital multimeter isn’t configured correctly for.
We must be aware of these common errors and ensure workers are properly trained on the specific type of DMM they are using.
We will now move to several other important safety topics related to DMMs that will continue to help us understand the importance of their certification, limitations, ratings, training, and the PPE we should be wearing for our protection.
A DMM Must Carry a Certification from a Nationally Recognized Testing Laboratory (NRTL)
Independent testing and evaluation are essential to ensure electrical equipment, appliances, and tools are safe to use within their defined intention and limitations under their “listed and labeled” certifications.
This listed and labeled certification is also required of DMMs because both the OSHA regulations and NFPA® 70E® standard require electrical equipment, including test instruments, to be used in accordance with their listed and labeled instructions.
This mandate by OSHA is found in 1910.302(b)(2) which states, “Installation and use. Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling.”
For NFPA 70E, this is found within the context of the seven mandatory criteria for a “Normal Operating Condition” to exist according to 110.2(B) Exception #1(4): “The equipment is used in accordance with instructions included in the listing and labeling and in accordance with manufacturer’s instructions.”
For hand-held DMMs and other similar portable test instruments, UL/IEC 61010-2-33 is the recognized standard that must be met. However, it is the responsibility of Nationally Recognized Testing Laboratories (NRTL) to conduct the actual testing of the device in controlled laboratories to determine if the product meets the stringent evaluation criteria. For DMMs, the NRTLs normally involved are UL (Underwriters Laboratories), CSA (Canadian Standards Association), TUV, and others who all specialize in testing and certifying DMMs.
Like all electrical devices that carry NRTL certification, after passing the rigorous testing, they will have earned the right to carry a label or marking indicating this accomplishment. Fig. 7 is a photo of the back of a high quality DMM showing the NRTL symbols of UL and CSA circled in red.
However, with an unregulated international supply chain flooding the U.S. and Canadian markets with cheap imitation products from China, Mexico, and other countries, users and buyers must be aware of counterfeit DMMs with bogus NRTL labeling. To minimize this risk, DMMs should only be procured through retailers and distributors with a proven track record for selling only genuine products.
OSHA has actual regulations pursuant to 29CFR1910.7 governing NRTLs.
Training in Test Instrument Operations Is Not Optional for Qualified Electrical Workers
As previously mentioned, the use of test instruments, including DMMs, is restricted to only qualified electrical persons, which is clearly established by NFPA 70E, 110.6(A): “Only qualified persons shall perform tasks such as testing, troubleshooting, and voltage measuring on electrical equipment where an electrical hazard exists.”
Most of us are familiar with the official definitions of a qualified electrical worker according to OSHA and NFPA 70E.
OSHA, under 1910.399 Subpart S, identifies a qualified person as, “One who has received training in and has demonstrated skills and knowledge in the construction and operation of electric equipment and installations and the hazards involved.”
But these two definitions alone are not enough. We must explore the governances much deeper to ascertain the specific training mandates to become a qualified electrical worker.
Anyone who has ever attended one of e-Hazard’s training classes can attest to the fact the definitions in and of themselves are just the tip of the training iceberg to become a qualified (electrical) person when exposed to electrical hazards energized at 50 volts or more. While I will not cover all the required training for qualified persons in this article, we will focus on those instructions that apply directly to electrical test instruments and test equipment.
Once again, both OSHA and 70E have additional training requirements specific to their safe use under the umbrella of a qualified person.
OSHA 1910.334(c) titled “Test Instruments and Equipment” establishes three directives:
- Only qualified persons are permitted to perform testing of electric circuits or equipment
- Test instruments must be visually inspected prior to use
- Test instruments and their accessories must be used within their rating and for the environment(s) they will be used in.
NFPA 70E’s training mandate for using test equipment takes a more comprehensive approach, but we must dig a little to uncover the training provisions for a qualified person under 110.4 “Training Requirements” as follows:
- The qualified person shall be familiar with proper use of…test equipment
- Must be qualified for certain equipment and tasks, including the use of test equipment
- The qualified person must also be able to:
- select appropriate test instruments
- demonstrate how to use the device to verify absence of voltage
- correctly interpret the data and
- understand all limitations for their use
As we can clearly see, training is not optional but a mandatory action. It is an essential part of being a qualified electrical worker according to the regulations and standards, and for good reason. Countless individuals have been seriously injured and killed while using or – more accurately – misusing test instruments, especially DMMs.
One last point regarding qualified persons must be briefly discussed. Did you notice none of the cited governances mention a single word about the “experience” of the worker? For instance, how long has the worker has been in the trade? Has he successfully completed an apprenticeship, college degree or job title such as “journeyman” or “electrical engineer” as prerequisites to be a qualified person?
No one will argue hands-on-field experience, vocational and/or classroom education are not important to help you perform your jobs, but experience or a degree alone does not necessarily mean a person can complete the job safely according to the regulations.
Most of us can probably recall one or more “veteran” or “old timer” we worked with who knew how to “git ‘er done” but was known to take shortcuts or failed to follow the safety rules in the process because they felt the rules were an unnecessary burden. After all, they were never injured, right?
But on the other side of the spectrum, the same can be said of green engineers fresh out of college equipped with a plethora of book knowledge but lack real-world exposure or a practical application of the learned theory. Therefore, being qualified versus experience or education are not mutually inclusive of one another, nor does the latter automatically fulfill the former.
Conclusion
These incredible inventions called DMMs are extremely helpful and needed in our profession, but they can also expose us to many hazards when we don’t understand or adhere to their safety instructions and limitations. This can only be accomplished through documented high-quality training by competent trainers.
This article series will continue to cover several other safety issues that must be considered when using DMMs along with some effective mitigation actions that will help reduce the chances of error, injury or equipment damage. We will also share some learnings of real events to help you avoid making similar mistakes.
