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'Extreme' engineer pays attention to details

Posted: 16 Jan 2007 ?? ?Print Version ?Bookmark and Share

Keywords:attention to detail in engineering? design for extreme performance? extreme design engineering? careful engineering? attention to detail in designing?

I've always been fascinated by engineers who push a design to a performance extreme in a selected dimension, such as resolution, absolute accuracy or power dissipation. These designers have to understand and analyze every source of error and shortfall, then work out a way around each without excessively compromising other factors. Call it a kind of "extreme scene investigation."

I first encountered this type of engineering more than 25 years ago in an article by Jim Williams, who is now staff scientist at Linear Technology. It discussed construction of a precise scale that was to be used by a nutrition lab for weighing newborns, every bit of food they ate and their "output." The scale needed resolution to 0.1oz and excellent absolute accuracy. Those specifications were achievable, albeit with effort. But then you added the next two: It had to use only standard, off-the-shelf components and never need calibration once placed in use.

Jim's article discussed how he uncovered every potential source of error in components, circuitry and system, and those due to stray currents and electromagnetic fields. He then methodically knocked each one down through careful engineering. At the time, high-resolution ADCs were expensive, idiosyncratic rarities; nor were there good, easy-to-use voltage reference ICs, among other deficiencies. As an example of how he achieved his goal, he used a standard bandgap reference, aged it, tested it to find the drive-current value where it had minimum drift and then ran it at that value.

To me, this sort of extreme attention-to-detail and successful design is part of the art and "existential pleasures of engineering," to borrow the title of Samuel Florman's excellent 1976 book. Overcoming first-order error sources, and then second- and third-order sources is a challenge for which many designs clearly don't have the luxury or need. But for those that do, it's engineering at its exhilarating ultimate.

For example, when developing ultra-accurate missile-guidance gyroscopes at Draper Laboratories, engineers used extremely precise tiny ball bearings, of course, to minimize gyro-wheel friction. But the residual friction was still too much, so they floated the entire gyro assembly in a high-density fluid to make the gyro buoyant and so reduce the effect of the wheel's mass on the bearings.

Good enough? Not quite. Since the density of the fluid varied with temperature, they kept the entire assembly at a specific temperature to eliminate yet another residual error source.

Most engineering designs today do not involve such extremes of performance. Instead, there's a more carefully nuanced balance among factors like overall performance, power, cost, size and time-to-market. In fact, in many applications, there's no point in exceeding a specification. After all, if you need to satisfy an industry-standard requirement such as the data rate for IEEE 802.n, exceeding that rate conveys no benefit. But sometimes it's nice to think about how you would design if you really had a focused goal on extreme performance and what it implies for engineering discipline and execution.

- Bill Schweber
EE Times

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