When two waves – sound, electrical, in water – that are of different frequencies are conveyed in the same medium, the alternating constructive and destructive interference gives rise to sum and difference frequencies. If acoustic tones are close to the same frequency, the resultant difference signal will be heard as a distinctive beating sound that […]
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Basics of intrinsically safe wiring
The National Electrical Code (NEC) distinguishes between classified and unclassified locations. Classified locations are potentially hazardous where there is electrical usage because the atmosphere contains or may due to mishap contain explosive gas, flammable liquid vapors, dust or flammable airborne material. The NEC specifies electrical materials, devices and installation methods for these areas. The requirements […]
Ten good internet sites for test engineers
You can often find the answer to a specific question or research an extensive area of interest on the Internet. Here are ten Internet resources that electronic professionals may find useful: 1. Wikipedia still has a reputation for providing fundamentals on just about any technical subject. Electronics has always been a focus, and as time […]
Understanding sampling rate
A large number of electronic components and systems are digital. Radio, TV and sound reproduction, to mention a few examples, have in recent years all gone digital, with increased precision and efficiency. The digital revolution has been nearly universal in today’s amazing oscilloscopes, where light-weight digital flat-screen models far outperform the old analog ancestors with […]
Magnetic flux density and magnetic monopoles
Flux in a magnetic circuit is analogous to current in an electrical circuit. This presupposes the fact that in magnetism, there is a circuit. The parallel to an electrical circuit is not absolute. In an electrical circuit there are two conductors, often called a hot conductor and a return conductor, which is frequently grounded. In […]
Basics of spectrum analyzers
At first glance, a spectrum analyzer closely resembles an oscilloscope, and in fact many contemporary advanced oscilloscopes incorporate built-in spectrum analyzers. An oscilloscope is primarily a time-domain instrument where signals are accessed by means of probes or cables connected to analog inputs. These signals display along two axes. The Y-axis represents amplitude in volts and […]
Why silicon and germanium are semiconductors
Both silicon and germanium can be used as the intrinsic semiconductor when fabricating solid-state devices. In the Periodic Table of the Elements, germanium (atomic number 32) occupies the position directly below silicon (atomic number 14). The Periodic Table of the Elements had been envisioned earlier, but its potential was more fully realized in the work […]
Scanning tunneling microscope vs. scanning electron microscope
The scanning electron microscope (SEM) is capable of imaging an object with a resolution of better than one nanometer. To put that in perspective, a meter is to the size of the earth as a nanometer is to the size of a marble. A nanometer, at the small limit of nanotechnology by definition, is a […]
Photomultiplier tube basics
The obvious superiority of solid-state devices has rendered vacuum tubes obsolete in most applications. But an important exception is the photomultiplier tube. It is an elegant assembly of metal substructures in a glass envelope, providing unprecedented low noise and high amplification at generous bandwidth. The inexpensive device can actually detect a single photon that enters […]
The difference between corona effect and St. Elmo’s fire
Corona effect, also known as corona discharge, is primarily a high-voltage transmission line phenomenon, but it is also seen surrounding lightning rods. Years ago, I was talking with a dairy farmer in Northern New England. We were inside his barn and had a clear view of the old farmhouse through the open door. It was […]