Decibels, (derived from bels, old units which, like unwieldy farads, are rarely used) are convenient and user-friendly terms for expressing the ratio between two amounts of power on a logarithmic scale or the amount of change, amplification or attenuation, over time of a single amount of power. In power and sound ratios, the factor is […]
Measuring and specifying microphones
One aspect of the work-at-home/stay-at-home environment of the past year has been an increased emphasis on podcasts, online meetings, and online video events. That’s why there’s more interest in microphone technology among those interested in producing a higher-quality experience. Here’s a short run-down on microphones and how they are typically measured and quantified. A microphone […]
Thanks, Pythagoras, for the basic science behind the theodolite
Pythagoras was a larger than life pre-Socratic philosopher, born on the island of Samos. The Pythagorean Theorem relates the lengths of the three sides of a right triangle. Undoubtedly the most familiar theorem in mathematics, it had been known previously in Mesopotamian, Indian and Chinese cultures, but it was elaborated, made part of the over-all […]
Antennas and antenna measurements
Most antenna designs operate via the resonance principle, which is based on the fact that electrons moving through a conductor reflect back toward the power source when encountering a discontinuity. When current, caused by a radio signal’s induced voltage, reaches the end of the antenna element, it is reflected, travels in the reverse direction, and […]
Don’t get zapped — Using test instruments safely
Most engineers think they’ve minimized the chance of nasty surprises around the test bench when they’ve grounded their instruments and perhaps kept one hand in their pocket when working around high voltages. That said, there remain electrical hazards that are less obvious. They involve the electrical wiring and the environment around the lab. To begin, […]
Basics of digital oscilloscope architecture
A digital storage oscilloscope (DSO) is characterized by the presence of a microprocessor, which is physically and functionally at the heart of the processing section. Other stages in the processor are the acquisition memory, at its input and the display memory at its output. The DSO’s signal paths (one for each channel) begin at the […]
Measuring the behavior of electronic filters
Passive electronic filters are composed of one or more passive components including resistors, inductors and capacitors. In contrast, active electronic filters also contain an amplifier composed of transistors or op-amps. The point of electronic filters is to pass some frequencies while blocking others. Depending upon the configuration, they selectively attenuate high frequencies (low pass), low […]
Non-solid-state inverters? There still are such things.
A device that converts dc to ac is known as an inverter. Nowadays, most engineers think of solid-state inverters in the context of applications such as electric vehicles and solar panels. Yet even today, not all inverters are solid state. One early form of power inverter was based on mechanical switching and was appropriately called […]
Transistor circuit configurations and Spice
In a recent post, we reviewed the basics of Spice circuit simulators. Most circuit simulations involve transistors, either as discrete components or within an integrated circuit. So it is useful to understand a few basics about how Spice models transistors. Transistors may have multiple states, typically saturation, cutoff, active and reverse. And transistors have an […]
When you can use Spice and its variants, when you can’t
It has been a long time since it was practical to breadboard even moderately complex IC designs to evaluate them prior to manufacture. This is particularly true because of subtle parasitic and characteristic impedance effects that rear their ugly head in the frequency ranges of many modern circuit designs. That is the rationale for Spice […]
