Most electrical hazards fall into three categories: Injury from electrical fire. Exposure to a blast caused by a line-to-line or line-to-ground arc fault. Electricians working on equipment in industrial settings where fault current is high may be injured or killed when close to an arc fault event even when electrical current does not pass through […]
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Mitigating shock, electrocution,
Basics of chemical batteries
The chemical battery resembles a capacitor in the sense that both are capable of taking a charge, storing electrical energy and releasing it later as needed, simply by connection to a load. But these devices work entirely differently. A capacitor can be idealized as consisting of two conductive plates connected to wire leads, separated by […]
Basics of electrical conduit
The first electrical distribution system provided direct current to residential and commercial customers in lower Manhattan. It was built by Edison Illuminating Co., beginning in 1882. Earlier in the century, telegraphy networks had become widespread, and ampacity, over-current protection and similar principles had been worked out. Fuses and even circuit breakers were available early in […]
Polyphase power basics and applications: what you need to know
Many homeowners and general handy workers know at least the basics of single-phase residential wiring and polyphase power. But three-phase work is mostly the domain of professional electricians who work in commercial and industrial settings where there are three-phase services, branch circuits, and motors. When one has learned the basic circuitry and equipment, actually three-phase […]
Basics of EM signal reflections
Signal reflection is a problem that arises when the cabling between devices or terminations at either end are substandard. This can happen in copper wire, in traces on a printed circuit board, in optical fiber. It is also a fact of life for wireless communication media where signals reflect from nearby objects and can arrive […]
Basics of TEM, TE, and TM propagation
Energy can propagate through a medium or through what is currently believed to be a vacuum. Propagation modes vary depending upon the type of energy and the nature of the medium. Consider sound: It can travel through any material, solid, liquid or gas. In air, sound consists of waves, discrete like a single click, or […]
Basics of aliasing in sampled waveforms
Aliasing can have different meanings depending upon the context. For example, in computer programming it refers to instances where a computer program uses two or more different labels in different parts of the program to refer to the same data location. If the location is modified using one label, the change may cause difficulties in parts of the program that […]
VIDEO: Using the Fluke 190-502 Scopemeter Math Functionality
The Fluke 190-502 Scopemeter is a battery-powered, handheld oscilloscope with lots of functionality in a small package. In this video we look at some facets of its Math mode and see how they differ from those in bench models.
Data recorders give NASA insights into Cessna crash tests
Test equipment from Diversified Technical Systems (DTS) gives researchers at the NASA Langley Research Center in Hampton, Va., insights during drop tests of a small Cessna aircraft meant to simulate a severe, but ultimately survivable crash. In August, a Cessna 172 plunged 100 ft at 55 mph and hit the ground, flipping over with a […]
Basics of Ethernet switches
In connecting computers to one another or to peripherals, the network switch has largely replaced the Ethernet hub, although the latter will still perform its intended functions. The difference is that the less advanced hub sends identical data between ports whereas the network switch (also known as a switching hub, bridging hub or MAC bridge) […]