Electrical TestersA¯i¿½i¿½WhatA¯i¿½i¿½s the Best Tester for You?
Published: July 2003
As the scope of electrical contracting expands, testing equipment evolves to meet changing needs. Testers today range from simple voltage testers to identify the presence of current, to a variety of sophisticated multifunction digital models for conventional electrical work, low-voltage projects, programmable logic control installations and other applications.
Dedicated voltage testers are the simplest electrical testing devices. They are designed to check voltage—the most commonly performed electrical test—and are available in models ranging from simple solenoid tools to sophisticated electronic instruments employing digital circuitry.
Some solenoid testers estimate the approximate level of voltage, but for precise readings, a digital tester is necessary.
“Individual preferences determine which type of voltage tester an electrician uses,” observed Chera M. Ellis, senior product manager at Greenlee Textron. “The basic functionality is the same among the manufacturers; the combination of functions, along with the safety ratings, varies.”
Whatever tester is selected, ruggedness and safety are two important features users look for, believes Mel Hendrickson, Amprobe application engineer. “These instruments are kept in pockets, often falling out and dropping onto hard surfaces; and they are carried tool boxes, where they are banged around with other tools. Still, they must accurately indicate the presence of voltage and be safe to use.”
In a world where digital devices rule, analog models remain the most-used type of voltage tester.
“Solenoid testers are mechanical tools that provide a tactile shake or vibration to confirm the presence of voltage in addition to the visible and audible means,” said Jim Gregorec, group manager, T&M Division, Ideal Industries.
“Many electricians have used them since they were apprentices, and they like their simplicity. Experienced users estimate the level of voltage by the amount of shake. In addition, solenoid testers are inexpensive, although there now are digital models with very attractive prices.”
Solenoid testers also bleed off ghost voltage, something electronic testers are unable to do. However, solenoid models heat up quickly, limiting the time for taking a reading, and requiring time to cool-down before the next test can be made.
Digital testers read a wider range of voltages, can provide accurate measurements and many models can perform other tests as well.
“Digital tester can provide more features for less cost,” said John O’Brien, applications engineer at Extech Instruments.
“Advantages of digital testers include continuous duty and better resolution of the voltage,” said Gregorec. “These testers have Cat III ratings and can distinguish between 208, 240 and 277 VAC systems.”
Tester leads and probes
Basic solenoid and digital voltage testers employ leads or probes that connect to the line being tested. Newer digital models use sensors that “read” voltage without making physical contact.
Types of leads and probes vary, based on needs and target applications, said David Wheaton, UEi product development director. “Some have a sharp tip that allows the technician to pierce the insulation to take readings where needed without severely compromising the insulation.”
Test leads usually are permanently attached to the tester.
“This reduces cost of manufacturing and prevents end users from losing them,” explained Amprobe’s Hendrickson. “Leads must be very flexible over a wide temperature range. Probes take the most beating on any voltage tester and in many models are made replaceable. In some cases they are covered with a moveable shroud that affords protection to the user.”
“Test leads and probes should be made of the highest quality material so that they are rugged enough to withstand the tough environment to which they are exposed,” noted Jason R. Wilbur, marketing manager, Fluke Electrical Products. Whatever the type tester or lead, Greenlee’s
Ellis emphasizes that it is extremely important that tester leads and probes have the proper measurement category rating.
“Make sure the leads are approved per UL 3111-1 or by some other test agency,” she advised. “A CE rating does not guarantee that an independent lab tested the leads.”
For both reliability and safety, it is important that leads are in good condition, said Jeffrey R. Jowett, Megger applications engineer.
“Worn leads become ‘leaky’ and interfere with accurate measurement and reliable performance,” he explained. “Hastily or carelessly substituted leads cause many accidents when applied to voltages where the tester may be adequately rated but the leads are not. Probes properly mated to the job increase speed and efficiency and improve reliability by eliminating problems such as contact resistance. But because they may be only considered accessories, leads and probes are frequently neglected.”
No-contact testers appear to be growing in popularity.
“Models with sensors in the tip eliminate the need to physically attach leads ... simply push a button to make the test,” said Ideal’s Gregorec.
Expanded testing capabilities
The most common capability beyond simple voltage test is continuity, said UEi’s Wheaton. “These models are either battery powered or store power from a voltage test then allows the technician to check for continuity by emitting a tone.”
In addition to providing voltage measurements, some testers can perform continuity tests, frequency, amperage, detect live conductors and perform GFCI tests, added Greenlee’s Ellis.
Depending on tester model, a variety of corollary measurements can be made, including current, frequency, resistance, conductance, capacitance and diode testing, said Megger’s Jowett. “Some models offer dual measurements of two parameters simultaneously, an aid in troubleshooting so that the unit isn’t tediously switched back and forth.
Relative functions enable the operator to measure only the difference between actual and base value such as 120V so that problem deviations are located more quickly and easily. Bar graphs are invaluable in detecting intermittent problems and also indicating a possible source of problem such as a loose switch. Fast-response buzzers make continuity testing of large numbers of circuits at a panel significantly quicker and less aggravating. Delay features override startup surges and wait until steady measurement settles in.”
A voltage tester will indicate the presence and approximate level of voltage. The next step, troubleshooting or evaluation of electrical systems, requires a multimeter or a specialty tester for that particular system, said ExTech’s John O’Brien.
“Increasingly,” said Fluke’s Wilbur, “residential and commercial electricians are testing fire alarms, audio/video systems, home security systems and structured wiring installations for whole-house automation, which require the use of an ohmmeter and/or low-voltage cable verification tool.
“Industrial electricians test variable-speed motor drives (0 to 60 Hz at non-line voltage levels), and programmable logic control (PLC) systems with various kinds of inputs and output signals that drive valves, relays, motor switches, etc.
Electronic voltage testers are a popular choice for checking for ‘on’ and ‘off’ conditions on triac outputs that drive relays.”
A dependable, accurate multimeter will perform a variety of tasks that will help isolate problems, Wheaton added. “This will give actual voltage levels to determine open grounds, reversed wiring and incomplete connections. Advanced meters are available that can log readings to observe circuit operation without watching the display.
Additional features are available at a much better cost. Meters continue to include multiple functions to meet the needs of the technician.
Specialized test tools are important. “While other models have resistance ranges—even to Megohms—only a genuine insulation tester provides the high voltage necessary to evaluate performance capabilities of circuits and equipment,” said Jowett. “Installation tests must be made on ground rods/electrodes, as well as periodic maintenance checks, and only a dedicated ground tester, not a generic ohmmeter, can fulfill this requirement.”
Clamp-on meters are very versatile because they quickly measure the three basic electrical parameters: volts, ohms and amps, Gregorec pointed out. “They can also measure capacitance and frequency. And, they have higher end features like ‘True RMS,’ ‘Peak Hold,’ and ‘Min/Max’ to accurately capture fluctuations in system power over a shorter-time frame. Datalogging capabilities enhance the recording capabilities of some meters which allow 40,000 records to be stored in the meter as the user can set time intervals from every half-second to five minutes apart. Datacomm, power quality, and grounding are all intertwined to ensure that equipment runs reliably and communicates reliably.”
Testers of the future
“Advances in non-contact current measurement have decreased the size of testers for taking current measurements without breaking the circuit,” said Wilbur. “Certainly incremental improvements will continue to be made, which will result in smaller, more capable testing devices. Advances in non-contact voltage and current measurements offer the greatest potential for further innovation.”
Ellis believes there will be a greater emphasis on safety and ergonomics in the next 18 months. “Measurement category ratings will exceed the minimum requirements thus giving the electrician peace of mind. The tester housing will be shaped to fit comfortably in the electrician’s hand so as to not cause any undo strain.”
Jowett believes the greatest changes are in the incorporation of data storage and download functions. “Because of miniaturization, additional features can be incorporated into a workable case size, so multi-function testers are more prevalent; microprocessors have improved basic measurement so that ranges and accuracies are better; and battery power is more reliable than it once was, including the prevalence of rechargeables.”
Concluded Gregorec: “Test tools continue to advance in performance at a rapid rate, consistently offering electrical contractors new innovations at a good price to make their jobs easier.” EC
GRIFFIN, a construction and tools writer from Oklahoma City, can be reached at 405.748.5256 or firstname.lastname@example.org.