Published: July 2005
Electricians routinely check for the presence of voltage. Simple analog testers long used to confirm whether a line is hot are giving way to more advanced digital instruments that can perform several other test functions.
Much has changed since the 2003 Cool Tools report about power testers when several manufacturers said that even in the digital age, analog testers were used more often than digital models.
From analog to digital
“Digital technologies are successfully replacing analog for testers,” said Jarek Bras, senior product manager at Amprobe. “Digital instruments have better features, increased recording capabilities, are, in general, less expensive than comparable analog meters, and prices are decreasing. In my opinion, the market for analog meters is going to disappear.”
While not everyone is ready to completely write off the familiar analog testers that shake and vibrate when they detect voltage, more and more electricians are turning to sophisticated, multifunction digital tools that are safe and easy to use.
Veteran electricians may be slow to replace their analog testers they have relied on since they were apprentices, but younger ones who grew up in a digital age are embracing the technology.
“Many electricians stayed with analog testers like those they started with as apprentices. They are comfortable using them and trust them,” said Jim Gregorec, group manager of the Ideal Industries T&M division. “One of a voltage tester's primary purposes is to ensure that you do not have voltage present before working on a circuit, so if that voltage tester states there is no voltage present, there better be no voltage present. Today, digital testers are growing in popularity with younger electricians coming into the trades who like more features and measurement discrimination. Digital testers also provide higher category ratings for increased safety.”
Jeffrey R. Jowett, Megger applications engineer, believes younger personnel find digital testers familiar, due to their educational background, and therefore are more comfortable using them.
“And readings,” Jowett said, “are given with digital accuracy, eliminating guessing of pointer position and parallax problems. In addition, digital testers are more durable-analog movements are very sensitive to dropping; digital models survive better.”
Fluke Corp. product specialist Duane Smith cited several reasons why digital voltage testers are becoming more popular.
“Most important is the measure of safety they provide over solenoid testers,” Smith said. “And digital testers are designed to take repeated high-energy transients without damage whereas solenoid testers do not stand up to the high-energy transients common in today's power distribution systems. Digital testers also meet current electrical safety standards while solenoid testers do not.”
In addition, digital testers bring other test functions that analog models cannot provide with capabilities varying by make and model.
“Multitesters are becoming more widely used because of advances in microcircuit design and engineering,” said John O'Brien, Extech technical support manager.
Portable digital power meters tend to be more universal, have more features, and come in smaller sizes.
“Basic power meters extend their capabilities to cover some of the more advanced PQ functions,” Bras said. “Very often they are designed to record data, and they are equipped with a generous memory, allowing recording through extended periods of time, and they have the ability to send data over the Internet or via wireless connections.”
According to Richard P. Bingham, director of product development at Dranetz BMI:
“Power testers continue to add additional functionality, such as increased number of parameters, graphical interfaces for each use, faster sampling rates for higher harmonic and frequency spectrum, decreased price per performance, and additional communication interfaces such as USB.
“With the addition of current, power- related parameters, including watts, VA, Var, kWh and PF can be computed. With multiple channels, parameters such as unbalance and phase rotation can be calculated. Harmonic and interharmonics calculations are becoming more standard, and even the flicker calculation from voltage fluctuations are more common. In addition, more instruments are complying with the IEC and IEEE standards.”
Leads and probes
Voltage testers offer a variety of leads or probes suited for various applications. Basic solenoid and digital testers have leads that connect to the circuit being tested; newer digital models have sensors to detect voltage without the need to make physical contact.
“Because frequently used testers may not have carrying cases, leads are more prone to frequent abuse,” said Ideal's Gregorec. “So leads on testers are typically beefier than more precise metering equipment, which is used less often. Probe tips are typically larger in diameter to fit into receptacles better.
“Finger guards and retractable probe tips are more prevalent today. Sensors give an approximate indication but not necessarily an accurate amount of voltage present, which you would see in a meter display.”
Says Amprobe's Bras: “A variety of current transducers are available with power meters. From small sizes-used for low-current applications ranging from below 1A to around 100 to 300 amps-through standard ones for 500A and 1,000A, to flexible CTs, capable of measuring 3,000A, 6,000A or even higher currents.
“Flexible CTs use the Rogowski measurement principle and have large internal diameters allowing clamping around entire bus bars,” Gregorec said.
Bingham said that flexible CTs are increasing in popularity and come in a wide range of sizes and current ratings.
“Split cores and clamp-on CTs continue to be used, ranging from 1A to 6,000A,” Bingham continued. “Hall-Effect CTs that can measure AC and DC currents are showing some signs of growth, as the DC offset in power systems, as well as measuring the DC bus current inside of equipment with AC-DC rectifiers, becomes a requirement. Voltage leads are evolving with increased emphasis on safety, such as keeping the hands a safe distance from the connection as well as integral fuses.”
Fluke's Smith said that there are many accessories available-including temperature probes and sensors-that extend the capability of a tester. That way, you can purchase a standard set of features in a tester, and, through accessories, you can add features not used regularly, but that are sometimes needed.
Megger's Jowett emphasizes that lead maintenance is critical.
“Leads,” Jowett said, “typically wear out much quicker than the tester, but are commonly overlooked. Measurement errors result from leaky leads, but the tendency is to suspect a problem with the tester. Leads must also have proper voltage ratings, again a factor often overlooked, that can result in injuries and fatalities.”
Match tester to application
Safe use of voltage testers begins with matching instruments to the applications for which they are used. Many have the opinion that safety factors provided by digital voltage testers make them preferable to analog models.
Chera M. Ellis, Greenlee senior product manager, believes multifunction electrical testers provide electricians with the ultimate in safety and performance.
Extech's O'Brian emphasizes the use of caution when working with voltages above 60V DC or 30V AC RMS.
“Before taking resistance measurements or testing continuity, disconnect the circuit under test from the main power supply and remove all loads from the circuit,” said O'Brian. “To avoid damage to an instrument, do not exceed the maximum input limits shown in the technical specifications. Do not use a meter or test leads if they appear damaged. Use extreme caution when working around bare conductors or bus bars-accidental contact with the conductor could result in electric shock.”
Ellis cites national statistics that electrician fatalities account for nearly one-tenth of all occupational deaths each year.
“Knowing what test or measurement tools to use can mean the difference between life and death,” Ellis said. “In light of these shocking statistics, it is interesting that many electricians use equipment that does not comply with any standard at all.
“These types of testers are available in the industry and should have a safety category rating of Category IV 1,000V. Category IV covers the highest, most dangerous level of transient over voltage that electricians are likely to encounter in utility service to a facility. For the electrician who works in Category IV locations, having appropriately rated test instruments is mandatory.”
Ellis said that instruments that meet the requirements of International Electrotechnical Commission (IEC) standard 61010-1 and national standards based on it such as UL 61010B-1 and C22.2 No. 1010.1, provide transient protection levels that are far above the instrument's maximum rated input.
This type of protection was not required in instruments designed to older standards such as IEC 348 and UL 1244.
“Without this additional protection against transient over voltages, which are becoming increasingly more common, serious injury or death can result,” Ellis said.
Testers for voltage and other power functions will continue to improve. Expect new models to be more compact while offering more features, better resolution, improved accuracy with increased use of wireless technologies and at prices that provide buyers with more value for dollars spent. EC
GRIFFIN, a construction and tools writer from Oklahoma City, can be reached at 405.748.5256 or firstname.lastname@example.org.