Published: February 2007
Testing for the presence of voltage is the most basic of electrical operations and can be performed by instruments ranging from simple solenoid tools that vibrate, indicating the presence of voltage, to sophisticated digital instruments that not only measure voltage with extreme accuracy but have multiple testing capabilities.
In a digital world, a surprising number of analog voltage testers remain in use. Experienced electricians who often began using simple solenoid testers as apprentices say they can estimate the level of voltage by the level of vibration of the tool.
Some in the industry say that the number of analog models on today’s jobs is declining as electricians turn to more accurate, easy-to-use digital tools available at very reasonable prices. The popularity of digital testers with multiple capabilities also is increasing.
Whatever the type of voltage tester selected, electricians want it to be safe, easy-to-use and reliable. Because users often carry testers in toolboxes where they can bump against other tools and in pockets from which they can fall onto hard surfaces, rugged construction is also very important.
Voltage tester options
But don’t count out the solenoid testers just yet. Scott Black, Extech Instruments product manager, pointed out that vocational and technical schools still include solenoid tests in electrical instruction programs.
“It appears the next generation of electricians will continue their use,” he said. “For ‘go/no go’ testing, there is no need to look at a scale since application of power creates a perceivable vibration and sound within the meter.”
Of digital testers, Black said additional features have been added in an effort to distinguish one model from another.
“Some models are available now that have an LCD display instead of lights to indicate the voltage level. Another has an LED light,” he added. “Technically, though, nothing has changed in the last three years.”
Spring Zhao, Greenlee Textron product manager, said that while still available, solenoid testers are not as widely used as digital instruments.
“Solenoid testers typically have very low impedance and thus do not pick up ‘ghost voltage’ like some of the high impedance digital meters do,” she said. “A solenoid tester is preferred over digital instruments in applications when an electrician does not need accurate voltage readings and is only looking for a simple way to check voltage. They are inexpensive and easier to handle since there are no batteries required to operate.”
Zhao said the latest developed voltage testers are more user-friendly with features such as automatic selection of multiple functions, including AC/DC voltage, current, continuity and resistance measurement. In addition to taking voltage readings, newly developed voltage testers have also added extra features such as vibration and sound to indicate voltage presence and GFCI test.
“The usage of multipurpose testers has increased dramatically in the past few years and the trend will continue in the near future,” Zhao said. “The most popular multipurpose models are testers with automatic function selection and Cat 4 category rating.”
Michael Stuart, senior marketing manager, electrical products, Fluke Corp., believes the numbers of solenoid testers are decreasing due to a greater focus on safety.
Many traditional solenoid testers have come under fire due to user safety concerns,” Stuart said. “Consequently, solid state, digital, category-rated Cat 3/600V or better testers are becoming the preferred and required basic testers. Some users may at first think there are circumstances where solenoid testers are still preferred. However, with advances made in today’s electronic testers—such as low impedance measurements, vibration indication and greater user protection—there are not many reasons to stay with a solenoid tester. And with digital models, we have seen a greater focus on user safety, while still maintaining utility. This means that the testers of today have the best of both worlds.”
Stuart said use of multipurpose testers is increasing. In addition to voltage, some available functions include continuity check, resistance (ohms) measurement, current measurement, GFCI trip, phase rotation indication and flashlight function. Which model is most popular depends on individual users and their requirements.
Jim Gregorec, group manager, T&M division, Ideal Industries, said solenoid testers remain popular because of their simplicity and ease of use.
“Many, he added, “have dual, independent circuitry so that there is always a backup voltage indication. With their low impedance, they also are not affected by ghost voltage. They do not require batteries to indicate voltage. Most have rugged test leads that have shielded probe tips for added safety.”
“These combination testers,” he said, “are among the most popular as continuity is a good test for verifying test leads are not broken, fuses are good and circuits are complete. A few specialty models also add a limited range of resistance and current measurements. Audible continuity is a very popular feature combined with voltage testers. Some even have microprocessor circuitry that can automatically display the current, voltage or resistance without having to select a function through the use of a dial.”
When evaluating testers, Gregorec cites several considerations:
1. Safety—Is the tester UL listed to Cat 3/600 volts?
2. Reliability—Electricians depend on the tester being right when it states that no voltage is present before work is started on a circuit—this is why the three-point test method should be used. Test a known circuit; test the circuit under test; test a known circuit again.
3. Ease of use—No dials and no multiple input jacks simplify use.
Tester leads Solenoid and digital voltage testers employ leads or probes that connect to the line being tested.
Types of leads and probes vary, based on testing needs and target applications. Some have a sharp tip that allows the technician to pierce the insulation to take readings where needed without severely compromising the insulation. Digital models use sensors that “read” voltage without making physical contact—simply push a button to make the test.
Test leads usually are permanently attached to the tester, which reduces the cost of manufacturing and prevents users from losing them. Leads and probes are frequently neglected because they are considered an “accessory” to the instrument. Worn leads can interfere with accurate measurement and reliable performance. 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 to improve reliability by eliminating problems such as contact resistance.
Leads should remain flexible over a wide range of temperature. Some are covered with a moveable shroud that provides a measure of protection to the user. Probes are subject to wear and are replaceable on many tester models.
Test leads and probes are always very crucial to proper testing, Fluke’s Stuart said.
“It is important that users know when their test probes or leads are damaged and when to replace them,” he said. “Always replace visibly damaged test leads and probes. Not all test leads and test probes are created equal. Heavy-duty test leads and replaceable test probes with a Cat 3/1,000-volt rating or better are preferred.”
Extech’s Black said safety must always come first.
“Test leads,” he said, “should meet the same safety category rating as the meter they are being used with. Exceeding these limits may cause bodily harm to the user and damage to the tester. Test leads and probes have to be built to stand up to the everyday use that they will be subjected to.”
Ideal’s Gregorec pointed out that test leads are the most prone tester component to experience abuse and damage. Therefore, it is important to have field-replaceable lead capability. Shielded probe tips minimize chances of arcing. Fused lead options further this protection.
“It is extremely important that the tester leads and probes have the proper measurement category rating,” Greenlee’s Zhao said. “Users should also make sure the leads are approved by a third party to the appropriate standards such as UL/CSA 61010. A CE rating does not guarantee that an independent lab has tested the leads. Depending on the applications, various test leads are used with different probe tips such as hook tips, pincer tips, various sizes of alligator clips, etc. It is always recommended to use test leads with the highest category rating, such as Cat 4, for taking safety measurements especially in an unfamiliar environment.”
Speaking of safety in general, Zhao believes the industry will see continuing improvements to push the envelope of tester safety ratings.
“Measurement safety ratings of Cat 4/1,000-volt testers will eventually become common. With the withdraw of the UL 1244 [old IEC standard] in January 2008, many manufacturers will need to invest more on tooling in order to have products that meet spacing requirements of the new IEC standard and with UL 61010-1.” EC
GRIFFIN, a construction and tools writer from Oklahoma City, can be reached at 405.748.5256 or firstname.lastname@example.org.