Without specifically mentioning Underwriters Laboratories (UL), the National Electrical Code (NEC) makes frequent reference to “a nationally recognized testing laboratory”(NRTL). There are several such organizations. UL is the best-known. Manufacturers submit their products to UL for evaluation. If they pass, the products are listed and/or labeled. Not all electrical products are required to be UL […]
Scopes that display spectrograms
The Tektronix MDO 3104 oscilloscope is called by the manufacturer a six-in-one instrument. Besides being a basic bench-type digital storage oscilloscope, it incorporates five other digital-based tools: spectrum analyzer, logic analyzer, function generator, digital voltmeter, and a protocol analyzer for serial data buses. The spectrum analyzer is traditionally a stand-alone instrument. It lets the user […]
X-rays and ionizing radiation
Electromagnetic radiation with a frequency between 3 × 1016 Hz (30 petahertz) and 3 × 1019 Hz (30 exahertz) falls into the X-ray category. The wavelengths are shorter than ultraviolet and longer than gamma radiation. Wilhelm Röntgen was the first to describe in detail this radiation, which he termed X-rays because they had been previously […]
Basics of lightning protection
The most effective counter-measure for lightning is adequate grounding in conjunction with surge suppression.
Arc welding basics
Arc welding differs from the soldering process in that the metals to be joined are melted to a significant depth. The molten metals mix along with filler material provided by a consumable electrode and when properly done the finished joint is quite strong. The soldering process, in contrast, consists of added material, traditionally a lead-tin […]
Here’s a rundown on free layout/PCB software
There are dozens of free PCB-layout and schematic packages available on the Web. Often they are stripped-down versions of more complex packages available for licensing. Often, the process of upgrading from freeware to more sophisticated versions is pretty easy. If your circuit needs are generally confined to relatively straightforward two-layer boards, here are a few […]
Four-way switch and three way switch: basics of wiring
Two three-way switches necessarily sit some distance apart, but electrically they constitute a single “black box.”
Basics of tantalum electrolytic capacitors
Like other electrolytics, tantalum capacitors cannot tolerate reverse polarity – the dielectric layer is destroyed leaving a highly conductive current path, and the device may explode.
Quantum tunneling and tunnel diodes
Quantum Tunneling is a quantum-mechanical phenomenon where a particle tunnels through a barrier that it classically could not surmount. It is the operative mechanism in tunnel diodes. Tunneling can arise with barriers of thickness around 1 to 3 nm and thinner. A simple barrier can be created by separating two conductors with an extremely thin […]
Space and time and the Lorentz transformation
Prior to Albert Einstein’s two theories of relativity, space was conceived as an inert, albeit multidimensional, frame of reference. It did not appear to move, but instead objects including earth moved through it. In the wake of Einstein’s revolution, physicists and eventually the general public came to see that space, along with time, was a […]