Note: The following is adapted from the book “ Electrical Engineering 101, Third Edition” by Darren Ashby (Newnes).

Do you remember your engineering introductory course? At most, I’ll venture that you are not sure you even had a 101 course. It’s likely that you did and, like the course I had, it really didn’t amount to much. In fact, I don’t remember anything except that it was supposed to be an “introduction to engineering.”

Much later in my senior year and shortly after I graduated, I learned some very useful general engineering methodologies. They are so beneficial that I sincerely wish they had taught these three things from the beginning of my coursework. In fact, it is my belief that this is basic, basic knowledge that any aspiring engineer should be required to know.

I promise that by using these in your day-to-day challenges you will be more successful and, besides that, everyone you work with will think you are a genius. If you are a student reading this, you will be amazed at how many problems you can solve with these skills. They are the fundamental building blocks for what is to come.

UNITS COUNT !

This is a skill that one of my favorite teachers drilled into me during my senior year. Until I understood unit math, I forced myself to memorize hundreds of equations just to pass tests. After applying this skill I found that, with just a few equations and a little algebra, you can solve nearly any problem.

This was definitely an “a-ha” moment for me. Suddenly the world made sense. Remember those dreaded story problems that you had to do in physics? Using unit math, those problems become a breeze; you can do them without even breaking a sweat.

Unit Math

With this process the units that the quantities are in become very important. You don’t just toss them aside because you can’t put them in your calculator. In fact, you figure out the units you want in your answer and then work the problem backward to figure out what you need to solve it. You do all this before you do anything with the numbers at all. This basic concept was taught way back in algebra class, but no one told you to do it with units. Let’s look at a very simple example.

When all the units that can be removed are gone, what you are left with is 60 mph, which is the correct answer. Now, you might be saying to yourself that was easy. You are right! That is the point after all – we want to make it easier. If you follow this basic format, most of the “story problems” you encounter every day will bow effortlessly to your machinations.

Another excellent place to use this technique is for solution verification. If the answer doesn’t come out in the right units, most likely something was wrong in your calculation. I always put units on the numbers and equations I use in MathCad (a tool no engineer should be without). That way when you see the correct units at the end of your work, it confirms that the equations are set up properly. (The nice thing is that MathCad automatically handles the conversions that are often needed.)

So, whenever you come upon a question that seems to have a whole pile of data and you have no idea where to begin, first figure out which units you want the answer in. Then shape that pile of data until the units match the units needed for the answer.

Sometimes Almost Is Good Enough

My father had a saying: “‘Almost’ only counts in horseshoes and hand grenades!”. He usually said this right after I “almost” put his tools away or I “almost” finished cleaning my room. Early in life I became somewhat of an expert in the field of “almost.” As my dad pointed out, there are many times when almost doesn’t count.

However, as this bit of wisdom states, it probably is good enough to almost hit your target with a hand grenade. There are a few other times when almost is good enough, too. One of them is when you are trying to estimate a result. A skill that goes hand in hand with the idea of unit math is that of estimation.

The skill or art of estimation involves two main points. The first is rounding to an easy number and the second is understanding ratios and percentages.

The rounding part comes easy. Let’s say you are adding two numbers, 97 and 97. These are both nearly 100, so say they are 100 for a minute; add them together and you get 200, or nearly so. Now, this is a very simplified explanation of this idea, and you might think, “Why didn’t you just type 97 into your calculator a couple of times and press the equals sign?” The reason is, as the problems become more and more complex, it becomes easier to make a mistake that can cause you to be far off in your analysis.

Let’s apply this idea to our previous example. If your calculator says 487 after you add 97 to 97, and you compare that with the estimate of 200 that you did in your head, you quickly realize that you must have hit a wrong button.

Ratios and percentages help you get an idea of how much one thing affects another. Say you have two systems that add their outputs together. In your design, one system outputs 100 times more than the other. The ratio of one to the other is 100:1. If the output of this product is way off, which of these two systems do you think is most likely at fault? It becomes obvious that one system has a bigger effect when you estimate the ratio of one to the other.

Developing the skill of estimation will help you eliminate hunting dead ends and chasing your tail when it comes to engineering analysis and troubleshooting. It will also keep you from making dumb mistakes on those pesky finals in school! Learn to estimate in your head as much as possible. It is okay to use calculators and other tools—just keep a running estimation in your head to check your work.

When you are estimating, you are trying to simplify the process of getting to the answer by allowing a margin of error to creep in. The estimated answer you get will be “almost” right, and close enough to help you figure out where else you may have screwed up.

In the game of horseshoes you get a few points for “almost” getting a ringer, but I doubt your boss will be happy with a circuit that “almost” works. However, if your estimates are “almost” right, they can help you design a circuit that even my dad would think is good enough.

Coming up in Part 2: How to Visualize Electrical Components.

©2012 Elsevier, Inc. All rights reserved. Printed with permission from Newnes, a division of Elsevier. Copyright 2012. For more information on this title and other similar books, please visit http://store.elsevier.com/Newnes/IMP_73/.