Electric Shock From Radios: A Review

During the 1930s, 1940s, and 1950s, Underwriters Laboratories did basic research in the field of safety and published the results of that research in a series of “Bulletins of Research.” At least 58 Bulletins w... Read More...

Body Resistance – A Review

This UL Bulletin of Research on the electric fence contains much information that applies to much more than just the electric fence. This is why it is a classic work.

On Limited-Current Circuits

A Product Safety Newsletter reader asked about where limited-current circuits are required by IEC 950, Sub-clause 2.4.1. He noted that a 5-volt DC circuit will give 2.5 milliamperes into the 2 kohm test resisto... Read More...
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Testing Purposes

Every product is subjected to a suite of tests. What are the purposes of these tests? Often, we just perform the tests as prescribed in a standard, and with whatever conditions are specified by the certificatio... Read More...
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Some Thoughts About Interlocks

Richard Nute is a product safety consultant engaged in safety design, safety manufacturing, safety certification, safety standards, and forensic investigations. Recently I’ve had occasion to consider the subj... Read More...
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Selecting a Fuse Value

Product Safety Newsletter - May/June 1990   Recently, a colleague asked, “How do I select the fuse rating for a new product?” His cord-connected product has a switching-mode power supply and consumes 170... Read More...
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The Hi-pot Test

The hi-pot test is another safety subject of which few of us feel comfortable that we are in control. What is the purpose of the hi-pot test, and what hazard does it address or obviate? First, each of the st... Read More...
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Characteristics of Air as an Insulator

A few months ago, we built a clear plastic box containing a four-inch square steel plane, a two-inch diameter steel sphere, and a micrometer drive to precisely adjust the distance between the plane and the sphe... Read More...
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Thermocouples and Temperature Measurement

One of our members suggested I write about thermocouples and temperature measurement. Textbooks have been written on this subject; I can only give a broad overview of the subject. Since temperature meaurement i... Read More...