Nuts & Volts - September 2004

In The Trenches

specifications that are mutually exclusive. Marketing replies that this is what the customer wants to buy. If we can't provide it, someone else will.

As you can see, specifications are the weapons that the engineer-ing/marketing war is fought with.

Instead of arming the photon torpedoes and targeting marketing, what can you do when faced with impossible target specifications? First, calm down. Remember, marketing is not engineering. Their idea of specifications is not the same as yours. It's really a different word and concept. They're simply repeating what the customer wants. Often, they've combined requests from different customers into a single product and it may simply be that they haven't reported the specifications accurately. Remember the three laws of selling:

1. Marketing is not engineering.

2. Marketing has a potential sale.

3. Everything in marketing is negotiable.

Turn Lemons into Lemonade

A/D is necessary. Price the system with the new A/D. You may need to create a completely new product because the existing one can't be modified. That may be an absurd approach, but examine it anyway. Try to anticipate every comment, criticism, and observation that marketing can make. Have a good answer for each and every one. Then call a design review.

In this review, explain in simple terms what impact the requested specifications have on the existing product and then present your design. Always have a workable design to present. It may not be cost effective or practical, but it is politically necessary. If you simply object to the design, you'll be considered an obstructionist.

If you provide an alternative design, you will be seen as a team player. They may complain about the cost or the delay or the form factor, but, if you have clearly explained your position and provided a design that meets the specifications, you will be seen as trying to help.

Note: You should generally just present your new approach. Let the questions lead you into com-

paring the new and old designs. Non-technical people generally find this easier to follow, but be completely prepared with graphs, tables, etc.

It often happens that, during this design review, new information or specifications emerge. In this example, the reason for 0.1 degree accuracy was because the product was to be used for measuring the body temperature of animals in a zoo. Since very few warm-blooded animals have a body temperature below 85 degrees and above 110 degrees, the eight-bit A/D can provide the 0.1 degree resolution required (256 steps in 0.1 degree increments gives a 25. 6 degree range).

Did you notice that we're talking resolution rather than accuracy? They are two entirely different specifications.

Unfortunately, they are often confused. The resolution of a system is its ability to separate close measurements. In this case, it's 0.1 degrees. The accuracy is the ability to measure according to a standard. This has not been discussed at all here.

Suppose you are given an impossible task. Let's say that marketing has promised a client a product that can measure temperature from 0 to 200 degrees F in 0.1 degree intervals using one of your standard products that has a simple, eight-bit processor.

Unfortunately, the processor only has an eight-bit A/D ( analog-to-digital converter). You need 2,000 steps (200 degrees by 0.1 degree intervals) and the A/D only provides 256 steps. It's impossible to do! (Actually, it may be possible if you employ the statistics we discussed a few months ago.)