The digital multimeter (DMM) is a basic tool among the wide variety of testers available today. Following, six multimeter manufacturers discuss the latest trends in this essential product category.
“The multimeter continues to hold an indispensable and essential role for electricians,” said Richard Wexler, marketing director, Flir Systems, Wilsonville, Ore. “The multimeter has yet to be replaced as the go-to, purpose-built, front-line diagnostic test tool. Nearly all electrical troubleshooting begins with testing and measuring parameters handled by multimeters. And now, newer, innovative capabilities further expand the versatility of multimeters with wireless data logging, productivity apps and built-in thermal imaging for infrared diagnostics.”
Wexler said essential measurement capabilities include alternating current (AC) and direct current (DC) voltage (including millivolts and low-impedence mode to manage ghost voltage), amperes (including milliamperes and microamperes), resistance, capacitance, frequency and continuity. True rms helps ensure accuracy regardless of the shape of the signal being measured.
Some all-new meters are being designed with increased accuracy in mind. For example, voltage measurement accuracy down to 0.09 percent was previously not available in handheld multimeters versus bench meters.
“Keep in mind, one other aspect of accuracy that can’t be measured with percentages is the meter’s ability to quickly and accurately hone in on the source of problems,” Wexler said. “Newer meters with infrared guided measurement allow users to see an actual thermal picture of electrical equipment, with overheating equipment becoming more readily apparent. This can help cut down troubleshooting time and ensure problem areas aren’t missed.”
Electricians are accustomed to managing productivity on smartphones and tablets, and some meters are keeping up with the move to a mobile-enabled electrical contractor. Wexler said features include larger, more sophisticated, full-color screens that are more in line with what electricians are accustomed to than a basic “calculator-style” LCD with seven-segment numerals. Newer thin-film-transistor (TFT) displays are easier to read and make it easier to navigate through menus for advanced functions like data logging and Bluetooth connectivity to mobile devices.
“Voltage safety ratings have not changed over the years, and It’s imperative to a meter that has CAT IV, 600V and CAT III, 1,000V ratings to ensure maximum protection during testing,” he said. “Multimeters with noncontact functions also improve safety. Infrared guided measurement in particular improves safety as a noncontact diagnostic method of showing electricians an actual image of potential hot spots from a safe distance, helping to take the guesswork out of anticipating hazards and avoiding injury. Noncontact voltage detection makes it easy to scan components and cables to verify they are not energized before work is performed.”
Ed Russo, regional manager, Hioki USA, Cranbury, N.J., said basic functions such as volts, amperes and ohms are common with all multimeter brands.
“Safety and quality are top features to look for,” he said. “Accuracy continues to get better, and some offer super-fast response rates. Technical people want their meters to feel good. A multimeter must be durable and easy to use and easy to view under real world working conditions. Look for a variety of models available, some with basic functionality, and some with extra functionality to suit the needs of the user. Look for exceptional features like noncontact voltage detection built into the multimeter.”
Russo said applications beyond the scope of a multimeter include power quality surveys, insulation resistance testing and automotive engine work.
John Olobri, director of sales and marketing, AEMC, Dover, N.H., describes the multimeter as the most basic and perhaps the most important tool for an electrician to carry day to day.
“True rms for accurate reading of non-linear waveforms are most important,” he said. “Other important capabilities are reading AC and DC voltage (750V AC, 1,000V DC), AC and DC current, millivolt range, 6,000-count display resolution, capacitance (100 millifarad) for motor starters, low-impedance setting for elimination of ‘phantom’ voltages, and min/max capture.”
For ease of use, Olobri said auto/manual ranging is a must and backlighting is helpful. Durability is a plus. For safety, an instrument should be CAT III, 600V rated and double-insulated.
“Temperature measurement can be considered a plus, and data logging is featured in some high-end models,” he said.
Jeff Jowett, senior application engineer, said multimeters are firmly entrenched with both field and bench-top workers and that they offer conveniences and ease of operation.
“Their small size alone is a notable advantage over most specifically dedicated types of testers,” he said. “The economy of basic-function models and the accuracy and resolution available from full-featured models will retain multimeters as a viable tool indefinitely.”
Jowett said true rms is now a predominant multimeter requirement, especially with the increasing number of circuits that have non-sinusoidal waveforms.
“Safety requirements now are a minimum IEC 61010 CAT III rating, with CAT IV preferred,” he said. “New construction materials for casework now make instruments more rugged for field work than they have ever been. However, look for actual data and not just a general claim like ‘rugged.’”
A safe isolation test should not be performed with the volts range on a multimeter.
“For that, a two-pole voltage tester should be used,” Jowett said. “Insulation tests require much higher voltages to pull a measurable amount of leakage current through good insulation. If more than basic continuity is required of a circuit test, more test current is required than provided by a multimeter. Standards and [standard operating procedures] often prescribe parameters that are more rigorous than a multimeter can provide.”
DMMs haven’t totally replaced analog multimeters.
Jowett said it is easy to recognize a moving analog pointer while digital instruments can only offer a rolling reading—a range of rapidly changing digits on a digital display. Many veteran operators prefer to see smooth pointer travel and can derive as much information from pointer movement as they do from individual digital readings.
Dave Kadonoff, field safety engineer, Ideal Industries, Sycamore, Ill., said there is great job diversity in electrical work, and depending upon the acquired discipline and skill set of a particular individual, multimeters may or may not be the most needed test tool.
“Over the past several years, advanced multimeters have added greater resolution, noncontact voltage detection, wider measurement ranges, but more significantly, connectivity,” he said. “Built-in data logging, Bluetooth connection to smartphones, remote displays and actively sending data to the cloud have all become fashionable and, in some cases, enhance job productivity greatly. But a drawback can be that a number of work environments prohibit bringing any transmitting or recording device onto the premises.”
While more functions are available on various test meters, these often do not come with higher resolution or accuracy.
“While the functions are often useful, cramming multiple functions into an already busy dial can be counterproductive,” Kadonoff said. “A case in point is there is a multimeter that includes insulation testing. The problem is that the meter itself is only a 2,000-count display, which makes interpreting readings more challenging.”
Kadonoff believes one of the biggest challenges for consumers is that the influx of low cost and often inexpensive meters has skewed the buying process.
“For longevity and for safety, it is highly recommended that any meter purchased have at least a CAT III rating (or CAT IV if required), be UL listed, come with silicone test leads and proper documentation,” he said. “Inexpensive meters often do not have any of these.”
What functions should buyers expect from today’s multimeters?
“Just about every electrical measurement you can think of,” said Chris Gloger, business unit manager, digital multimeters, Fluke Corp., Everett, Wash. “The ability to measure electrical phenomenon has followed the trend in computing, where more capability is now available than ever before. The key is for multimeter manufacturers to implement this power in a way that is beneficial for the DMM user. That means implementing new measurement capabilities behind a simple, easy-to-understand interface. And, for the user, it means looking for a DMM that offers the functions specific to their particular job.”
Rather than looking for a DMM that has 20 or 30 dial positions to cover every possible measurement, Gloger said users should look for a DMM with measurement functions that fit their common tasks. ECs might be more interested in rapid go/no-go (noncontact) testing for voltage presence, and low-impedance modes for preventing false readings caused by ghost voltage.
“A DMM can measure almost any electrical parameter, but most users do not need to measure everything; they need to measure specific things extremely well,” he said. “So users should be able to find a DMM that meets their specific needs.”
Many manufacturers now are including wireless communications capability in their DMMs.
“This is a trend that is going to continue,” Gloger said. “The instrument takes a single, momentary measurement and makes it recordable and storable in a database. Several good things happen at this point. An electrician in the field can instantly transmit results to a main office. A report of the day’s work can be completed on-site and emailed to the customer. And readings from the last visit can be compared to current readings for signs of wear or degraded performance. It takes the contractor’s role up a level, from being a reactive crisis solver to a proactive maintenance professional.”