How does a manufacturer verify that a TV, a microwave oven, a cordless phone, or a computer is safe to use? Since safety testing is not a well-established area of technical expertise, we asked six of our readers who specialize in safety testing to discuss the tasks they perform and the significance of their responsibilities.
Unlike many other segments of the electronics industry, there are no master’s degree programs in large universities and no national association of consumer product safety test engineers. The nearest equivalent is the IEEE EMC Association’s product safety test group, and its leaders hope that the discipline will, some day, achieve full recognition. But even without such status, safety testing is an extremely important function.
From our interviews, we learned safety testing has a common theme: electrical shock, mechanical/physical hazard, low-voltage/high-energy exposure, and fire. Other aspects, such as protection of a child from sharp corners, are addressed for specific products, but these four risk areas form the nucleus of successful safety test programs.
Why test for safety? Companies have a legal responsibility to provide safe products, and obviously, this is a prime motivator. In addition, the need to satisfy customers is a significant driving force. You want to know that the products you buy will not injure you.
The proof of product safety comes in the form of a symbol. In the United States, the well-known Underwriters Laboratories (UL) symbol is the mark of choice. The Conformite Europeene approval, symbolized by the CE Marking, is the European assurance of safety as well as the product passport allowing equipment into the 18-nation European marketplace. To that end, our interviews revealed that much of the safety-test emphasis culminates in the right to use the coveted UL and CE symbols on products for retail outlets.
We Aren’t There Yet
Stroll through any large store and look at the symbols of product safety on electrical products. The UL symbol is most evident, which isn’t surprising since it went on more than 16 billion products last year alone. The mark of the 106-year-old institution indicates that a certain level of compliance with UL standards has been verified.
The UL achieved its position as the de facto standards group for consumer products because it stepped forward with a needed service and developed a strong presence. In the same way that IBM set the de facto standards for computers and AT&T defined local and long-distance telephone service, you, your parents, and your grandparents have turned to the UL for an assurance of safety.
For example, a recent visit to a local retailer revealed a Belkin battery backup that had been blessed by the UL. Black & Decker steam irons and toaster ovens had the same marking, as did a Hoover vacuum cleaner, a Sanyo apartment-sized refrigerator, and a Sunbeam mixer.
In recognition of the European market, Belkin’s battery backup also had the CE Marking, as did a Hewlett-Packard ink-jet printer, a Compaq computer, and a Korea Data Systems computer terminal. Sharp’s microwave ovens sport the UL symbol plus an indication that they meet the FCC limits for radiated RF.
Surprisingly, several products had no safety symbols. Why? Possibly the manufacturer saved a few cents on each by bypassing the safety test. But is it worth the gamble?
Microwave-Oven Safety
In the search for people in industry involved in product safety test, one of the closest equivalents to a certified professional was Derek Shannon, a safety test engineer at Sharp Electronics in Memphis, TN. He came into the safety test arena with an E.E. degree 13 years ago, not quite knowing what to expect in his assignment.
It wasn’t easy to get information then, and things haven’t changed much in that respect. “There is one bright spot, however. UL has many seminars on a variety of safety-related topics,” he noted, “and that has been my best technical resource.”
Sharp has five production lines for microwave ovens at Memphis, and the production test station on each line includes hipot test to stress insulation at voltage levels far beyond what would be encountered in normal use. It also has a complex-looking but extremely functional microwave leakage tester.
“The test system has about 30 sensor probes that surround the operating oven,” Mr. Shannon continued. “If any one of the probes detects a leak that exceeds the UL recommended limits, it automatically stops the sequence and notifies the operator of the problem and its location.”
The microwave-oven test organization at Sharp has earned the coveted UL Total Certification Program. “In this arrangement, the UL authorizes us to perform tests and apply the UL symbol. They audit us periodically,” Mr. Shannon reported, “and every three months, UL checks a random sampling of ovens. A complete follow-up test can take as long as 10 days.”
How has safety testing changed in 13 years? “The tests themselves are similar to those when I started,” Mr. Shannon reported, “but the test equipment on the market is better, smaller, faster, and more automated.”
A creative engineer can find a way to automate test stations. “We needed the measurement capability of a Keithley Instruments’ microohmmeter,” Mr. Shannon said, “but wanted automatic switching to speed up the test. We found a contractor to incorporate meters into the test configuration, and now they are part of each production test station.”
Testing Laundry Equipment
Maytag makes several types of home laundry equipment in its plant in Newton, IA. About 12 years ago, the company combined safety tests for all products into one organization managed by Tom Riley, a mechanical engineer in the design department. “We have the UL-certified laboratory status and run most of the safety tests ourselves,” he noted. The UL audits our results periodically.”
Every product is subjected to a hipot test before shipment. Additional safety tests are run on equipment as defined by the UL. Maytag personnel perform detailed safety tests on samples from the production line, and UL periodically asks to have safety tests repeated for its observation. Once a year, UL engineers conduct an audit review.
What has changed in the past 12 years? “On most products, the scenario has stayed fairly constant,” according to Mr. Riley. “On clothes dryers, however, we added some what-if tests a few years ago, including an evaluation of what happens if the heating element becomes shorted to the case.”
For products for the European market, Maytag has not elected self-certification. Instead, it goes to outside testing agencies for authorization to use the CE Marking.
Safety Test Potpourri
Specialists at several other companies also put safety testing on a pedestal. The product may be an uninter-ruptible power supply (UPS), an air conditioner, an electric shaver, or a church organ. Here are some examples:
Power Supplies
Sola/Hevi-Duty manufactures constant-voltage power supplies, UPS, and regulators at several locations. “We were certified by UL and did our own safety testing with spot checks by its engineers,” according to Dale Corel, product design engineer at the Ft. Payne, AL, location. “But that wasn’t practical. Now UL handles all safety testing except for 100% hipot and ground-bond checks. The ground-bond test verifies that, if the insulation fails, the grounding circuit will protect the user from shock.”
The company sells in Canada, and UL certification is supplemented by an induced-voltage test on all units. On equipment sold in Europe, the company self-certifies and uses the CE Marking.
Air Conditioners and Dehumidifiers
In a huge facility in Edison, NJ, Frigidaire Home Products manufactures 2,000,000 air conditioners and dehumidifiers a year, and the UL symbol goes on each unit. “UL checks one in every 10,000 products,” said Fred Bhalman, a quality engineer. “Some are tested at our plant, and the others get a more extensive going-over at a UL laboratory. We also do three levels of hipot tests and low-voltage testing on all products plus a leakage current check to simulate the impedance of a human body.”
Church Organs
Allen Organ in Macungie, PA, supplies more church organs than any other company in the world. About 40% of its electronic pipe organs are shipped to other nations. “All of the electrically powered subassemblies in our products are certified by UL,” said Jeff Radcliffe, a test manager. “We do hipot tests on subassemblies and work with UL on additional safety tests.”
Electric Shavers
Most of the shaving equipment and other personal-care products with the Remington name are manufactured outside the United States. A few basic safety tests, including hipot, are run on all products. “All our labs, both foreign and domestic, are UL-certified,” according to Pete Olenoski, a quality control engineer. “UL engineers monitor our testing to verify that we are conforming to their standards, and from time to time, they will take a few products to their laboratory for validation.”
The Bottom Line
Even without an official safety test organization with channels for communications and standardization, there is a remarkable correlation among these specialists. The UL is their unifying agency, and this system does produce results.
Published by EE-Evaluation Engineering
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November 2000