The interface electronics for the LVDT must excite the primary-side winding with a sine wave and then demodulate the two resultant secondary-side waveforms; modern ICs make this analog-signal process fairly straightforward. Part 1 of this FAQ looked at the basics of LVDT excitation, demodulation, and waveforms. This part looks at two standard ICs which implement […]
LVDT electronics, Part 1: Excitation and demodulation
The interface electronics for the LVDT must excite the primary-side winding with a sine wave and then demodulate the two resultant secondary-side waveforms; modern ICs make this analog-signal process fairly straightforward. The first two parts of this LVDT article (see References) looked at the LVDT transducer itself, along with its attributes and history. This second […]
Optical tweezers move nano-objects, Part 3: The system
Part 2 of this article continued the exploration of the basic optical tweezer. This part builds up to a complete system, DIY optical tweezer systems, and extensions to the basic optical-tweezer arrangement. The optical tweezer is obviously not a simple system, and a complete system requires lenses, dichroic mirrors, a laser, video camera, isolation against […]
Optical tweezers move nano-objects, Part 2: The optical path
A combination of optics, lasers, electronics, and combined with advanced physics principles, allows “touch-free” physical manipulation of molecules, viruses, and other nano-sized objects. Part 1 of this article presented the goals of the optical-tweezer design and some of the reasoning which leads to it. This part continues to build up to a larger, complete system. […]
Optical tweezers move nano-objects, Part 1: The Principles
A combination of optics, lasers, electronics, and combined with advanced physics principles, allows “touch-free” physical manipulation of molecules, viruses, and other nano-sized objects. How do you manipulate and move tiny objects such as pieces of DNA or living cells? Conventional mechanical or vacuum tweezers, no matter how small, couldn’t grab them and would cause damage […]
Kelvin 4-Wire sensing solves the “IR Drop” problem
Novice engineers usually don’t learn about this problem and its solution in school, but “practicing” ones learn about it soon enough! Problem: I need to determine the change in resistance of a low-resistance sensor located many meters away. My plan was simply to apply a known voltage across the thin-wire sensor leads and measure the […]
LVDT position sensor, Part 2: Characteristics
The linear variable differential transformer (LVDT) is a widely used, inherently rugged, linear-position sensor offering accurate and consistent performance over a wide span of distances. Part 1 of this FAQ looked at the basic operation of the LVDT. This part looks at some of its other performance attributes and characteristics. Q: What does an LVDT […]
LVDT position sensor, Part 1: Basics and principles
The linear variable differential transformer (LVDT) is a widely used, inherently rugged, linear-position sensor offering accurate and consistent performance over a wide span of distances. Sensing of physical position is among the most commonly needed parameters in industrial, military/aerospace, robotics, scientific measurement, and control applications, and there are many sensors in use to accomplish this. […]
Westinghouse and the fail-safe train air brake, Part 4: Post-Westinghouse
The story of Westinghouse Electric and affiliates does not end with its bankruptcy, but it does change dramatically. It is a twisting tale of getting into new markets, abandoning old ones, having some successes, and having some abysmal failures, which completely transformed what remained. A few of the many highlights and developments include: setting up […]
Westinghouse and the fail-safe train air brake, Part 3: Electric brake control
The man who brought fail-safe brakes to railroads once had a major role in the 20th-century industry, but a combination of events and decisions have left only his braking system as a recognized legacy. Thus far, we have looked at the classic, and still widely used fail-safe pneumatic brake (Part 1 and Part 2) However, […]
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