9/11/2016 Cool Tools: Clamp Meters | EC Mag
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Published: February 2012Clamp meters continue to evolve. Overall, there is awelcome migration of advanced capabilities frommultimeters to clamp meters, said André Rebelo, globalcommunications manager of Extech Instruments(www.extech.com/instruments), a FLIR company. Newfunctionality of the current clamp meters, he said, makeelectrical work easier and safer to perform with fewertools.
“Tool integration is a key theme of the future of testequipment, and advanced clamp models offer that futureglimpse today,” he said. “Advances also have broughtincreased accuracy and performance expectations toclamp meters. Related to that, many more clamp meters
offer true rms accuracy, ensuring that electrical readings from equipment with nonsinusoidal waveforms are asaccurate as readings of clean, sinewave power form the main source.”
Market research company Frost & Sullivan forecast two years ago that multifunctionality would be a major trend inhandheld testing equipment, Rebelo said.
“That has been borne out in clamp meters with the promise of multifunctionality fully realized in today’s advancedclamp meters,” he said. “Models have been introduced that integrate capabilities typically found in separate testequipment. Examples of integrated functionality include contact and noncontact (infrared) temperature, dualtemperature measurement, noncontact voltage detector, ‘recording’ or data logging, and sophisticated datafunctions previously found only on multimeters. Onebutton differential temperature calculation can quickly identifyabnormal temperatures in two components. True rms measurements expand ‘accurate versatility’ by deliveringprecise readings even when electrical signals are distorted by electronic or solid state components, such as newer,efficiencyoriented motor controls.
“Additionally, significant advances have been made in coordinating clamp meter readings with other essentialdiagnostic tools such as infrared thermal imaging cameras,” he said.
Rebelo cited several clamp meter developments and features:
• The increased prevalence of direct current (DC) power in everything from industrial motors to residential lightinghas increased the need for a DC clamp meter. Having both alternating current (AC) and DC measurement in oneclamp meter can be indispensable.
• Bluetooth data transmission of essential electrical readings to related tools, such as infrared cameras, increasesaccuracy of coordinated findings and simplifies and accelerates work by eliminating the need for notetaking.
• Miniclamps with ultracompact jaws make it safer to work in confined areas, such as a conduit junction or elbow.
• Safety has been increased by the increased availability of clamp meters with a CAT IV overvoltage rating for usein demanding environments. Higher current ratings also have safely expanded the capabilities of clamp meters ashigh as 1,500amperes (A). Flexible clamp meters have been around for several years, but they remain useful forhardtoreach areas and large wire bundles with current ratings upward of 3,000A.
“An entrylevel clamp meter should be rated for 400A AC current, AC/DC voltage, resistance, frequency,capacitance, temperature (using a thermocouple), duty cycle, as well as diode and continuity testing,” Rebelo said.“Having a builtin voltage detector is a plus that can often be found in many basic clamp meters. It’s important tokeep in mind that overall, socalled ‘standard clamp meter’ offerings have migrated upwards so that it is reasonablefor an electrician to expect more from a basic clamp.
“Advanced models forge ahead as a showcase of innovation in test equipment. Bluetooth wireless technology cantransmit electrical readings to a compatible thermal imager that can imprint readings right on a related infraredimage. We see parallels of what’s taking place in consumer electronics—related devices are working together and‘talking to each other.’
“Topoftheline models offer higher CAT IV overvoltage ratings and higher current ratings and generally are largerand more rugged with jaws that can swallow a 750 MCM conductor or two 500 MCM conductors. Faster processing
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9/11/2016 Cool Tools: Clamp Meters | EC Mag
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permits the capture of important yet brief incidents such as inrush currents and transients.”
John Olobri, AEMC (www.aemc.com) director of sales and marketing, cited functionality and operator safety amongthe most significant improvements in clamp meters.
“We see more meters today meeting the CAT IV safety ratings,” Olobri said. “Several clampons now offer the abilityto perform power and harmonic measurements, temperature measurements, inrush and more. Multiline displaysmake it easier for the operator to see several variables at the same time, such as volts, amps and watts. Datacommunication to computers makes it easier for the operator to document test results.”
Olobri defined basic functions of clamp meters for everyday use to include measurements of volts, amps, resistance,continuity, backlighting of the display, and a hold function. Highend models offer the ability to measure power,power factor total harmonic distortion and indi vidual harmonics, inrush, phaserotation measurements, and theability to do limited data logging.
Christopher Bohn, Fluke Corp. (www.fluke.com/clamps) electrical products marketing manager, said that clampmeters remain the goto tool for electricians measuring loads, such as motors, since amperage is the most importantmeasurement for load assessment, and a clamp meter directly measures and reads in amps, while also being ableto measure voltage and other parameters.
Improvements to current clamp meters have been developed in response to electrical work environments, he said.
“Electricians reported frustration with the limitations of classic clamp jaws,” he said. “They were unable to work thejaw into tight cabinets and around large, rigid conduit. Improvements made to meet that need include flexible currentprobe attachments, detachable clamp jaws, and detachable remote displays.”
Bohn cited other improvements in the past few years that continued increases in safety ratings to meet NFPA 70Erequirements, development of highaccuracy milliamp clamp meters for use in controls/automation, and dual AC/DCcapability, now more common in response to increased DC measurement applications.
According to Bohn, a basic, safetyrated AC digital clamp meter measures amps using the current transformer builtinto the jaw and measures voltage using test leads. Advanced models include additional features and measurementcapabilities such as inrush for capturing readings at motor startup, filters for accurately measuring variablefrequency drive output, and flexible current probes or removable display technology.
“Today’s clamp meters better account for the hazard and difficulty of the live electrical work environment,” Bohn said.“The innovations previously cited allow an electrician to easily connect around the measurement point and then toremove his or her hand from the live electrical environment to take the measurement. And accuracy continues toincrease, while cost has remained flat or decreased for products of far higher overall quality and feature set.”
Jim Gregorec, Ideal Industries (www.idealindustries.com) business unit manager, said that clamp meters continue toconsolidate multimeter functionality and incorporate more easeofuse features, such as auto ranging; auto zeroing;and brighter, bolder displays.
“Accuracy,” Gregorec said, “has increased slightly, while safety has been maintained at high levels with the adventof category safety ratings. Costs have increased modestly as global economies come out of the recession. I thinksome of today’s meters are more robust from the effects of noisy circuits and electromagnetic interference. Bettershielding and frequency rejections above the 50/60 hertz fundamental have made for easier circuit troubleshooting.Low amp ranges have made it possible for larger amperage clamps (i.e., 600A/1,000A) to accurately measurecurrents around 1A.”
He said a basic clamp meter should be able to measure AC amperage, AC/DC voltage, resistance, and continuity ina CAT III, 600V environment.
Higher end models add measuring capabilities and ruggedness/durability.
“For example, higher end clamps can also measure capacitors on motors, frequency of voltage/current, and add DCcurrent capability for solar and industrial measurements. Higher end models can also withstand many more voltagetransients, heavygloved use, and overall wear and tear of the mechanical and electronic components,” he said.
Ian Bensted, Megger (www.megger.com) product manager, said that mechanics within the clamp jaw haveimproved, giving greater accuracy at lowcurrent measurements.
“A number of clamp meters today have true rms, giving greater accuracy with distorted sinusoidal waveformscapability as well as a DC current function,” Bensted said. “Most have a simpletouse function dial that renders idealfor singlehanded use. Also, the features on clamps today mean very little reference to the user manual is required,as the features are selfexplanatory.
“Several units are capable of voltage, resistance, capacitance and frequency, making them more a multimeter typeinstrument. These additional features are now accepted as the norm with prices remaining much as they were twoyears ago. CAT safety ratings in a few models are now up to CAT IV, 600V.”
With the selection of clamp meters available today and the additional features they offer, Bensted said it is difficulttoday to define a basic clamp meter.
“A prospective buyer for a basic clamp meter generally is only too happy to find their purchase is capable ofadditional functions if required,” he said. “Today a clamp meter is usually chosen for its additional features versuscost.”
GRIFFIN, a construction and tools writer from Oklahoma City, can be reached at 405.748.5256 or up[email protected].
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