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, […]
Westinghouse and the fail-safe train air brake, Part 2: The solution
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. Part 1 established the need for a reliable, fail-safe braking system. This part looks at the system design in more detail, […]
Westinghouse and the fail-safe train air brake, Part 1: The problem
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. Some innovations seem so obvious and pervasive that we assume they have always been with us, but, of course, that is […]
Sorry, but it’s “Goodbye, Caboose” – EoT devices have made you obsolete, Part 2
Part 1 of this article discussed the concept and basic implementation of the end of train (EOT) device. This part explores the EOT and its larger “ecosystem” in more detail. First, a bit of history While the first caboose replacement was a simple flashing rear-end device (FRED), first used by the Florida East Coast Railroad […]