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 […]

## Difference between measuring resistance and conductivity

Generally, an electrical conductor is a long solid rod, often insulated. It may be rectangular, like the electrician’s bus bar, irregular in cross section, or it may be merely a conductive path through the atmosphere, created by a process of ionization. Most electronics professionals have measured the resistance of conductors typically using a volt-ohm meter. […]

## Are you sure you know what bandwidth means?

Bandwidth is a principal specification when choosing an oscilloscope or related instrument. What it means in this context is a displayed signal’s maximum frequency above which the scope attenuates the amplitude of the signal it sees. Problem is, this isn’t the only definition of bandwidth. The concept has slightly different meanings (and consequences) depending on […]

## Subtleties of math functions in digital storage oscilloscopes

One of the great innovations in modern oscilloscopes is the Math mode. Even in many inexpensive scopes, it generally takes three forms: Dual Waveform Math, FFT, and Advanced Math. Dual Waveform Math requires two waveforms displayed in separate channels to function, but aside from that, it is quite simple. You just run a couple BNC […]

## Working with oscilloscope probes, part two

The oscilloscope can be viewed as essentially a voltmeter that incorporates a dynamic display. But the oscilloscope can also make use of a current probe to convert current information into corresponding voltage potentials displayed in units of Amperes. The current-to-voltage conversion takes place within the current probe which operates like the electrician’s clamp-on ammeter. The […]

## Basics of oscilloscope probes – Part one

Engineers know what an oscilloscope probe is. It basically permits the user to measure the voltage at any terminal or wire and display the waveform. It usually incorporates a needle point that is capable of getting into a tight place without shorting out to another pin, wire or grounded surface. And it can be equipped […]

## A fractional Fourier Transform? Yes, there is such a thing.

The Fourier Transform, outlined by French mathematician and physicist Joseph Fourier (1768-1830) in The Analytic Theory of Heat (1822), asserted that any function of a variable, whether continuous or discontinuous, can be expanded in a series of sines of multiples of the variable. His focus at the time was the propagation of heat in an […]

## The difference between measuring magnetic flux and magnetic fields

Simply stated, a magnetic field is analogous to electrical voltage, while magnetic flux is analogous to electrical current. A magnetic circuit is analogous to an electrical circuit with important differences. Electromotive force in an electrical circuit corresponds to magnetomotive force. Resistance and its reciprocal, conductance, in an electrical circuit corresponds to reluctance and its reciprocal, […]

## Basics of CMOS and measuring CMOS logic parameters

Complementary metal-oxide semiconductor (CMOS) fabrication uses p-type and n-type complementary and symmetrical pairs to implement logic functions. The fundamental building block of the CMOS circuit is the MOSFET semiconductor, which enables it to operate at far lower current levels than bipolar transistors. This current reduction comes via pairs of p-type and n-type MOSFETs connected gate-to-gate […]

## Hysteresis and its measurement

Hysteresis might be defined as something that happens when the physical state depends upon its history. The classic example of hysteresis in action is the residential thermostat. It has built-in hysteresis to prevent rapid cycling. It’s low cut-in and high cut-out levels are designed to prevent the heating/cooling system from rapid switching, which would quickly […]

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