Cool Tools: Clamp Meters
Published: September 2010
From a basic testing device providing nonintrusive measurement of electrical current without interrupting its flow, the clamp meter has evolved into a multifunction test tool with capabilities comparable to multimeters.
From yesterday’s analog models, today’s clamp meters have entered the digital age. Compared to those sold only a few years ago, these clamp meters not only provide more measurement functions, but they are more compact, lighter in weight, and easier to use.
There is a broader selection than ever before after several toolmakers added testing equipment to their product lines. With many product options to consider, it is important to evaluate and compare specifications and features that are important for the ways the tester will be used.
Representatives from four leading test tool manufacturers offered the following observations about clamp meters available today.
AEMC (www.aemc.com), John P. Olobri, director of sales and marketing, said: “Today’s clamp-on meters are all far superior to those offered in the early 2000s. In addition to current measurement, most, if not all, clamp-on meters on the market today measure voltage, resistance, continuity and frequency. Higher end models also offer the capability of measuring temperature phase rotation and power.
“Typical accuracies are in the 0.1 to 0.2 percent range, where in the past, 0.5 was normal. Multifunction capabilities have also greatly improved to include some functions found in basic power meters, such as watts and volt-amperes. Some models also offer the ability to store measurements and communicate with data-analysis software on PCs.
“Clamp-on meters are extremely easy devices to use. Most, if not all, functions are available by simple switch selection. Measurement results are immediately displayed on a digital screen. Several meters offer dual displays capable of showing multiple parameters at the same time. A great deal of attention has been placed on durability and safety with meters capable of measuring in the thousands of amps. The need to address operator safety has had a positive effect on the meters offered today with most classified in the 600-volt, Cat III or IV rating area.
“The availability of multifunction single-chip components has reduced the barriers to entry for competitors to near zero. This increase in the number of suppliers has caused market prices to be lower than in the past.”
Extech Instruments (www.extech.com/instruments), Andre Rebelo, global communications manager, said: “Clamp meters continue to evolve with multifunctionality being the key differentiator, and higher accuracy continues to become accessible even with more basic clamp meters. There also is increased interconnectedness among clamp-on meters and other test equipment as they become part of measurement systems.
“Even among basic models, clamp meters offer a respectable mix of measuring and testing capabilities that a contractor might expect to find in his digital multimeter. In addition to noninvasive AC or AC and DC current measurements ranging up to 400A, minimum features to expect include AC/DC voltage, resistance, capacitance, frequency (and duty cycle), temperature (using a Type-K bead probe), diode test voltage, and continuity. Many entry-level meters feature a 2,000-count display.
“When an electrician looks at a stream of constantly changing readings, one-button data functions can help to make sense of what was discovered in an extended measuring period. Functions also can help identify ‘minimum/maximum’ values and ‘peak hold’ to capture in-rush surges. Other useful features are ‘data hold,’ which freezes a reading on the screen, and ‘relative’ mode to zero- out the meter to a particular threshold.
“Let’s face it. An electrician is using a clamp because he wants a multimeter that does more, and as a result, the clamp-on meter has become the Swiss army knife of test equipment. Built-in tools, like a noncontact voltage detector, infrared thermometer, and dual bead probe thermometer, contribute to substantial advances in clamp-on meter versatility. In quarter one this year, we introduced a Bluetooth-enabled clamp-on meter.
“Today there are clamp meters that are designed for particular markets. HVAC-oriented clamp meters may have a microamp test function for flame rod testing, for example. There also are milliamp process meters with compact jaws that are designed for tight spaces, with increased resolution down to a milliamp.
“Additionally, several other features available today add to the versatility of clamp meters by eliminating the need for additional instruments or tools. For example, some entry level miniclamp meters have a built-in flashlight to improve illumination. From these compact models through top range clamp meters, a built-in noncontact voltage detector helps electricians quickly identify live wires before starting a job without the need for a separate voltage detector.”
Fluke Corp. (www.fluke.com), Chris Rayburn, clamp meter marketing manager, said: “Fundamentals of measurement have not changed much; however, features once only available in higher end models are now available in most entry-level units. What’s different is the type of multifunction capabilities included in most of today’s clamp meters. Some models take the approach of including features for a specific work set, such as a facilities tech. Both satisfy job needs and reduce the number of tools needed as well as reducing complexity. Other models that offer all features all the time face ease-of-use challenges.
“More clamps with power quality features are now available, and the average price for those higher end models has dropped.
“In the application realm, most technicians now interact with nonlinear electronic controls or equipment, requiring true RMS clamp meters for accurate measurement.
“State-of-the-art signal processing ensures stable, repeatable measurements in electrically noisy environments. Thin jaws are very important to many users’ applications, and a swivel clamp is very popular because of the flexibility to view measurement readings from various angles.
“Durability and safety in some brands has also improved over time with many clamps now rated Cat IV. However, other brands are still not tested independently (UL) to the ratings, or drop-tested and subjected to extreme use to verify durability.
“Competition affects prices. There’s a large market size to draw from, and hand tool suppliers, for one, are looking to expand and grow their markets by offering electrical test products. More Asian suppliers are looking to penetrate U.S. and European electrical markets. Competition helps level the playing field for the lower cost, price-sensitive market space. In general, prices are now lower and products have more features.”
Ideal Industries (www.idealindustries.com), Jim Gregorec, T&M business unit manager, said: “Basic clamp meters offer small, tapered jaws that can make it easier to separate a single conductor from a nest of wires in an electrical panel and can measure voltage, current and verify continuity.
“Due to the simplicity, compact size, and cost, 400A AC clamp meters are the most popular clamp meter with residential electricians, while 600A AC clamp meters are most prevalent with commercial/industrial electricians.
“Minimum capabilities should be measuring AC current from 1A to 200A along with audible continuity and one and two ranges of voltage and resistance. This would allow many installation electricians to consolidate to one test tool for everyday use. Service electricians would require more functions and ranges and additional test tools.
“Noncontact voltage (NCV) for quick power checks is a step-up feature that is being found on some less expensive clamp meters. Higher end models have more functions, such as capacitance and frequency through the jaw measurements. Higher safety ratings and durability are paramount in commercial/industrial/utility environments.
“Multifunction and accuracy have sufficed through the years while ease-of-use and safety have improved significantly. With the increased speed and lowered costs of microchips in recent years, auto-ranging has become the standard. With the advent of category ratings added to meter safety standards in conjunction with NFPA 70E, today’s meters are built to a higher safety level. Understanding the working environment, [the] PPE required, and [the] safety of hand test tools is key to working safely.
“There are more companies adding clamp meters to their product lines as the barrier to entry is low, given the wide availability.
“A basic clamp meter ensures all three phases on your feeders are pulling the same current.
“An advanced clamp meter with some logging capability, will help resolve intermittent breaker trips.
“A specialty clamp meter is used for maintenance on production conveyor motors, plant air compressors, and HVAC motors when knowing inrush current is crucial to keep these systems running.
“We have not seen a lot of downward pricing pressures because it is recognized that there is more to a clamp meter than meets the eye. Improved safety, quality of construction, and reliability of electronic components inside the meter show additional value over time to professionals. Unique features on some models have real value to end-customers. Lastly, service needs to be part of the equation. Whether it’s application help or calibration or repair, electricians on the job need to be able to rely on knowledgeable inside and outside technical support that meets their needs.”
GRIFFIN, a construction and tools writer from Oklahoma City, can be reached at email@example.com.