Semi-wireless instruments, failures, historian costs
Readers weigh in and ask questions about articles and multi-media
Re: Back to Basics: Using 'semi-wireless’ instrumentation, Nov. 2009
I recently completed a semi-wireless installation and my research had revealed exactly what you discussed in your column. I was hoping to find a total wireless solution for a radar level transmitter on a remote fuel oil tank. Because of the power requirements of radar level transmitters, a complete wireless solution was not economical considering the cost of a solar panel and rechargeable battery setup. Fortunately, an existing 120 Vac circuit ran underground past the tank to receptacles at the unloading platform.
The power source originates from an unmanned pump house located about 200 feet from the tank. This project was prompted by a safety concern for steam plant operators who had to trudge out to the tank once a shift, often through knee-deep or higher snow, climb the stairs to the top and 'stick’ it.
Scott A. Somers, process control engineerKatahdin Paper, East Millinocket, ME
Get what you pay for
Re: Opinion: Do you need a $60,000 process historian? One SQL expert says no, 03/26/2009 News
I would like to know who’s process historian are you buying for $5k and how many tags. I doubt you are going to buy a historian with a “full blown” SQL Server 2005 for $5k from Rockwell, OSI PI, GE, Wonderware, or any of the other people that play in the large process area. So, give some examples.
Darren Ash, engineer, Birmingham, AL
The way I see it, it’s a matter of choice: On one hand there are proprietary historians that have made most of the important choices for you, leaving a few “wizards” and dialog boxes to complete a configuration. This is a perfectly valid pick for companies that have minimal requirements and just want to plug it in and move on. On the other hand is the increasing number of tech-savvy companies that want their historian integrated deeply and seamlessly in their corporate processes. Sure it takes a little more up-front effort, but such companies realize that the dividends pay out perpetually, making the additional effort extremely rewarding.
Dennis Runo, system integrator, Mesa, AZ
Nice try but I think you missed the mark with this one. A process historian can be had for as little as $5,000 and that includes a full copy of MS SQL Server 2005. But the author oversimplifies the effort involved in creating and maintaining a process historian. How long would it take to create 10,000 tag references in his $5,000 system? What happens if the applications in the field change? Sure you can create your own database and use SQL inserts but there is a value in having an optimized data schema. It’s like comparing a little red wagon to a minivan. If a company’s data is so insignificant that it is only willing to invest in a wagon, it should reconsider why it’s collecting the data in the first place.
Customer investment is difference
Re: How to avoid project failure, Nov. 2009
My company was the system integrator for a network of military-deployed communication vehicles. While [the prototype] stage was a success, the effort was ultimately scaled back and put on hold. Of the reasons you listed, two stuck in my mind. First was a lack of client involvement and second was frequent changes in requirements and specifications. The client was flaky and non-committal to some decisions early on, and it was reflected in the constant revision of system documentation and the comments after reviews. Even after prototyping, key components were still being hashed out. This, of course, describes the second point of changing requirements and specifications. At the time, our engineers’ fingers were pointed at our customer. I realize now, through the experience and as a pupil of project management, that the burden of failure fell just as equally, if not more so, on our own management. Failure to take some of the steps you describe diminished our ability to work with the customer effectively and define project goals. I wish my managers had a crystal ball, or this article.
Domenic De Rubis
Video tutorials provide basics
Re: CEtv Video instrumentation tutorials
I really appreciate your videos in basic principles for sensing, measurement, and control. They clearly demonstrate concepts useful for those entering a field or just needing an occasional refresher.
Kim Fowler, president
IEEE Instrumentation & Measurement Society
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