Ask Control Engineering
The Ask Control Engineering blog covers all aspects of automation, including motors, drives, sensors, motion control, machine control and embedded systems. Control Engineering answers questions from readers of Control Engineering's print and online magazines, newsletters and other publications. To comment on any blog posting, click on the post's highlighted question and scroll to the "Post a Comment" box at the bottom. Submit questions as comments to any existing post.
Is each day is really shorter?
Dear Control Engineering: I heard something about the recent earthquake in Chile affecting the earth’s rotation. What’s that about?As strange as it sounds, NASA believes that the movement of the tectonic plates of the earth that caused the earthquake in Chile on February 27 has shifted the position of the earth’s axis and its rotation has speeded up. The Jet Propulsion Laborat ...... Read More
Comments (0)Working with resistive sensor elements
Dear Control Engineering: I’ve read that RTDs (resistance temperature detector) are often the most precise temperature sensing devices. Given the relatively narrow range of resistance involved, how is it practical to get precision with two, three, or more decimal places on a Celsius scale? Sensors that measure a process variable using changes in resistance extend beyond RTDs. Thermistors al ...... Read More
Comments (1)Induction motors with autotransformers
Bruce Konzak writes:Dear Control Engineering: Does a single phase 240 Vac induction motor have the same performance characteristics when powered by an autotransformer with a line to neutral feeder, as it does when powered normally by a line-to-line connection 120 degrees out of phase? I’m having some trouble getting consensus on this one. We put the question to Joe Pottebaum, senior applica ...... Read More
Comments (1)Five tips for designing control panels
Dear Control Engineering: When planning control panels, what are key design considerations? Here are five points to keep in mind as you begin: 1. Consider the purpose and goals of the machine that the control panel will serve. How can the next-generation design further those goals? 2. Use hardware and software components and industry standards to speed control panel design, assembly, test, and ins ...... Read More
Comments (0)How do hackers invade networks?
Dear Control Engineering: I was reading the posting about hackers invading control systems. How is that possible with safeguards? One of the techniques that has been in use with hackers for a while is “phishing,” which is a way for the hacker to gain access to a system by fooling a human being into unwittingly creating an access point. Usually you get some kind of email with an attac ...... Read More
Comments (0)What’s the point of twisted-pair wiring?
Dear Control Engineering: I see references from time to time that certain types of cables have “twisted-pair” conductors. Why should I care if the wires are twisted or not? The quest to eliminate the electromagnetic interference that gets picked up by signal cables dates back to some of the earliest uses of electrical communication. The first telephone systems used the same wiring te ...... Read More
Comments (1)Tiny bubbles in the molasses
After watching our video tutorial on level sensing with a bubbler, Bob Scheich of K & P Sales Engineers, Golden, CO writes: “I am a manufacturer’s rep that sells level sensors. I have an application at a bakery that has molasses in a tank that is 10 feet tall by 20 feet long. Would a bubbler work in that application, or does the viscosity of the liquid cause the pressure to incre ...... Read More
Comments (0)What’s happening with nuclear waste?
Dear Control Engineering: You seem to be a proponent of nuclear power, but you never discuss the problems related to nuclear waste. Radioactive and nuclear waste is a pretty big category since there are so many different kinds of it. But if we’re going to discuss nuclear power generation, the most relevant type is classified as spent fuel. This is what’s left over when a reactor has ...... Read More
Comments (1)Are hackers breaking into industrial systems?
Dear Control Engineering: I was reading the article Control System Cyber Security Worries. I don’t believe we’ve ever been hacked, but I know there have been break-ins at some places. I keep hearing a story about a sewage release caused by a hacker, but I’ve never known if that’s true or just a fish story. Are hacks at industrial sites happening all the time and we just ...... Read More
Comments (0)Motor control terminology clarified
Dear Control Engineering: I have another one of those confusing terminology questions. Is a servo motor amplifier the same as a servo motor drive? Yes, sort of. Amplifier (amp for short), inverter, adjustable-speed drive (ASD), and variable-frequency drive (VFD) are all terms generally used to describe the motor controller or the motion controller that adjusts motor speed, among other functions. L ...... Read More
Comments (0)Future nuclear powerplants
Dear Control Engineering: With interest in nuclear power growing again, are we likely to see new technologies emerge? Even though construction of plants in the U.S. has been minimal, has research and development been going on? The traditional nuclear power generating technology that we’re familiar with is the pressurized water reactor (PWR) that dominates the industry. The commercial instal ...... Read More
Comments (1)Burning up wireless bandwidth
Dear Control Engineering: A while back there were predictions that the growth of online video watching would clog the Internet. Apparently it didn’t(?). Now there are similar predictions for wireless internet bandwidth. What’s actually happening? Fortunately, wired Internet bandwidth capacity managed to keep pace with online video growth, at least for the most part. In any case, the ...... Read More
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