Engineering application design*

Winter 2000 Topic/Project:
Unit of Measure Conversion

Simple conversion:
lb => kg

Complex conversion:
ft^3/hr => kg/day - requires density

Over the next several months, this topic will be discussed at length, as it is fundamental to engineering applications design.

It should be noted: "this is by no means the only way to solve this problem, nor is it necessarily the best way. The key is, it is somewhere to start. And for the lack of any thing else...lets begin..."

If anyone has any suggestions, please feel free to email them. They would be greatly appreciated and welcomed.

Our goal:

"Design a unit conversion module in Visual Basic 6.0"

When designing engineering applications, one can not overlook the importance that units play when designing algorithms.

One would never think of adding 15 lb to 40 kg without first converting to a common unit base, of either lbs or kg's. If this step is ignored serious complications arise. As was seen recently with one of the NASA Mars space probes that missed its target. Why? Because someone forgot, or missed, a unit conversion, resulting in an incorrect calculations. The cost? Astronomical, in both time and money.

As we define the problem we will see just how complicated unit conversions are. It is impractical to think that we will consider every type of unit conversion, but we want to cover as many possibilities as practical.

In the process, we want to design a module that is both functional and extensible. Thus, as our requirements grow we will have an algorithm that will be easy to maintain and expand.

So lets begin with the obvious:

The problem:

At first glance, converting units of measure may seem quite trivial. Yet, as we investigate the problem we quickly realize that it is actually quite complex.

e.g. types of conversions:

Simple linear conversion:
2.2 lb = 1 kg (approx.)

Conversions requiring a scale change:
F = 9/5 * C + 32

Complex conversions requiring additional parameters:
lb/hr = ft^3/hr * density (lb/ft^3) (mass flow = volume flow * density)

The problem is made more complex because the algorithm must allow for the reciprocal unit conversion.
e.g. 2.2 lb = 1 kg and 0.45 kg = 1 lb (approx.)

Not to be forgotten: As more units conversions are added we need to take into account all possible combinations for unit within a give type.
e.g. Weight
2.2 lb = 1 kg
16 oz = 1 lb
1000 g = 1 kg...etc

Much more to come...So please come back soon...

If you have any comments or tips that you wish to share please feel
free to email them.

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