Three Things They Should Teach in Engineering 101

Lesson Number Three

This article will wrap up the three most important lessons I have learned as an engineer. I re-arranged the order somewhat from lesson number one as I realized the importance of understanding lesson two to fully comprehend lesson number three. By the end of this installment, you should be able to really understand what is going on inside a circuit, and visualize how it works.

I reiterate my promise; if you can truly implement the following techniques it will generate nothing but success in your efforts.

Engineering 101, Intuitive Signal Analysis

I'm not sure if this is actually taught in school. This is my name for it, and it is something I learned on my own in college and in the workplace. I didn't call it an actual discipline until I had been working for a while and had explained my methods to fellow engineers to help them solve their own dilemmas. I do think, however, that a lot of so-called 'bright' people out there use this skill without really knowing it or putting a name to it. They seem to be able to point to something you have been working on for hours and say your problem is there. They just seem to intuitively know what should happen. I believe this is a skill that can be and should be taught.

The first thing you need for intuitive signal analysis is experience, lots of it. You need to 'get a feel' for how different components work. You need to spend a lot of time in the lab and you need to understand the basics of each component. You need to know what a given signal will do as it passes through a given component. Remember the physical equivalents of the basic components? These are the building blocks of your ability to visualize the operation of a circuit. You must imagine what is happening inside the circuit as the input changes. If you can visualize that, you can predict what the outputs will do.

The second thing you must do is to drill the basics. For example, what happens to the impedance of a capacitor as frequency increases? It goes down. You should know that type of information off the top of your head. If you do, you can identify a high pass or low pass filter immediately. How about the impedance of an inductor? What does it do as frequency increases? What does negative feedback do to an op-amp? (See the Product Engineering archives for a lesson on this.)

The third thing is to break the problem into smaller chunks that can be handled easily. By doing this, the problem or solution to the problem can be found and identified. Do you remember the 'step input' function? You should be able to describe the reaction of any part of your circuit to this input.

One thing you do not need to know is what the output will be precisely. You do not need to memorize every equation in the book to intuitively know your circuit. But you do need to know what effect changing a value of a component will have. For example, given a low pass RC filter and an AC signal input, if you increase the value of the capacitor, what should happen to the amplitude of the output? Will it get smaller or larger? The answer is smaller, and exactly how much depends on the frequency of the signal and the time constant of the filter. What happens as you increase current into the base of a transistor? Current through the collector increases. What happens to voltage across a resistor as current decreases? These are simple effects of components, but you would be surprised at how many engineers don't know the answers to these types of questions immediately.

I believe it is necessary for a person to spend a lot of time in the lab to develop this skill. If you look at the response of a lot of different circuits a whole bunch of times you will 'learn' how they should act. When this knowledge is integrated, a wonderful thing happens. Your head becomes a circuit simulator. You will be able to sum up the effects caused by the various components in the circuit and intuitively understand what is happening. Let me show you an example.

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