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Repost: The varied and graphically-intensive world of nomograms March 3, 2013

Posted by mareserinitatis in electromagnetics, engineering, geology, geophysics, grad school.
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I spent a good chunk of time yesterday dealing with Smith charts, and I remembered in the recesses of my brain that I had once posted something about them in the old blog.  Sadly, it wasn’t as technically intensive as it could have been, but I still decided it was fun enough for a repost.  If you would like to read something with a bit more technical content, you can check out Fluxor’s post on Smith charts at EngineerBlogs.

A nomogram is an incredibly useful tool. It is a visual “solution” to an equation. Usually it is some sort of chart or plot that allows you to figure out “what you’ve got” and you can move from there to “what you need”.

Anyone who works on the analog side of electrical engineering often gets to play with Smith charts, which were of course invented by Baker*. They’re rather confusing looking things:

The usefulness in Smith charts is that they can allow you to determine things like how much more transmission line you need to get an impedance match in your device. Rather than trying to solve an equation using complex values, you can just move along the curve in a Smith chart. (Disclaimer: While I learned how to use Smith charts in my microwave engineering course, I unfortunately would need to spend some time with my buddy Pozar to remember how to do it now.) I’m also aided in my negligence by the fact that there are a lot of nifty software programs that will compute the necessary values, reducing the necessity of using a Smith chart. (Thank goodness for computers. If it weren’t for computers, I’d probably have to learn how to use a slide rule, too.)

What brought this up is that I was introduced to a nomogram used by scientists in the field of paleomagnetism. The nomograms in this case showed relationships in demagnetization of magnetic minerals. For instance, if you have a mineral that has been exposed to a temperature of 400°C for 1000 seconds in the lab, you can follow the line on the nomogram and discover that the same amount of demagnetization could be caused by sitting in a temperature of 350°C for 100 million years.

So why do I spend time mentioning this on my LJ? Could it be because knowing that there are graphical methods to approximate solutions to problems is good to know? It is good to know, but it’s not why I bring it up. The reason I felt the need to post about it is because I had an entirely different picture of nomograms when I was sitting in class:

tastee nom-o-grams

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*Just kidding. It was developed by Phillip H. Smith.

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