The Hall effect, first described by Edwin Hall in 1879, results in an electrical output when a thin metal plate is immersed in a magnetic field of sufficient strength. The magnetic field must be perpendicular to an electrical current conducted through the plate. The Hall effect voltage potential depends upon the strength of the magnetic […]
FAQ
When RMS amplitude is important and when it isn’t
There are a variety of ways to specify the amplitude of a waveform. Here are a few of the most common forms and a primer on when specific types are most appropriate. In physics. amplitude is the absolute value of the maximum displacement from zero during one period of an oscillation. In electrical waveforms, amplitude […]
Detecting gravitational waves
Gravitational waves were first proposed by Henri Poincaré in 1905 and further described in Albert Einstein’s 1916 General Theory of Relativity. Gravitational Waves are powerful perturbations of the space-time continuum. However, the sources of gravitational waves we know about are enormously distant and therefore faint by the time they reach earth–like EM radiation, their intensity […]
Testing vulnerabilities in programmable logic controllers
Had you examined the controls handling automotive assembly lines before the mid 1970s you would have found cabinets full of relays, cam timers, drum sequencers and hardwired controllers. All these controls had to be swapped out or modified to handle line retooling during a model-year change. To reduce the cost of such changeovers, General Motors […]
The difference between noise and jitter
Electronic noise and jitter are closely related phenomena, but they are not the same. While noise typically manifests as amplitude distortion, jitter pertains to timing of digital signals. Either of them may be caused by outside interference or internal sources. Noise can be seen in an oscilloscope time domain display as a noticeable thickening of […]
Basics of spectrometers and spectroscopy
The spectroscope is an instrument that separates white or near-white light into constituent colored bands as in a rainbow. The spectra can be projected onto a screen, viewed through a lens assembly, or photographed. The most elementary spectroscopes consisted of a single prism as used by Isaac Newton, described in an early treatise. He caused […]
Basics of measuring fuel cells
A fuel cell converts oxygen or another oxidizing agent and hydrogen or some other fuel into electricity and heat. A third byproduct, depending on the fuel used, is methane or another non-earth-friendly substance. But the most basic fuel cell combines hydrogen and oxygen to produce pure water. This simple, long-lasting device with no moving parts […]
Measuring efficiency in solar photovoltaic cells
Single-junction solar cells have a maximum theoretical efficiency of 33.16%, the Shockley-Queisser limit. But there are work-arounds that permit solar array designers to surpass that limit on a square-foot basis. The maximum solar conversion efficiency of around 33.7% happens at a 1.34 eV band gap and is subject to several assumptions. By way of review, […]
Up close and personal with magnetrons
Today most people’s experience with a magnetron is as a source of microwaves in residential microwave ovens. The microwave radiation is conveyed to the oven section via a waveguide. Microwave ovens are also a favorite target of scavengers and experimenters who like to take things apart. The magnetron is one frequently scavenged component. You can […]
The back and forth of interferometer technology
Conceptually, the interferometer is a relatively simple instrument that compares two distances typically differing only by a slight amount. Two waves, often coherent light waves, reflect from standard mirrors mounted at the object under investigation. The light from one mirror passes through a half-silvered mirror while the light from the other reflects from the back […]
