Let's start off with another esaeP's fable. Once upon a time, there was a King who told his Courtiers, "Send up the Royal Wizard." The Wizard promptly came running up, asking, "Sire, what is your desire?" The King said, "Make me invisible." So the Wizard went down to his cavern, got his book of potions, brought up an Eye of Newt, a Wing of Bat, and all of the other good things he needed, and went to see the King. He sprinkled the right potion and incanted the correct phrase and, presto, the King was INVISIBLE. The King's robes and crown kept moving around the throne room, but the King himself was invisible. The whole court was impressed. Good stuff! Good magic!
The next morning, the King awoke early and roared, "Get that lousy wizard up here." The Wizard came running up, in fear for his life, as soon as he got the word. "Sire, what is the problem?" The King replied, "Dammit, I asked you to make me invisible, but I'm still bumping into things." End of fable.
Think about it. The Wizard did what he was asked to do, yet he didn't get a satisfied customer. The King specified what he wanted, yet when he got what he asked for, he was unhappy.
Does this ever happen with your customers? How can we avoid this in the future? It sure takes much better communication than the King had with his Wizard. Perhaps the Wizard should ask what the King was trying to accomplish. What did he really want?
Here's something to think about: Do you ever ask your customers what they really want? And are you then prepared to give them what they really want, rather than what they said they wanted?
For example, once an engineer at company A went out for a bid on a signal conditioner circuit, and he defined the function he wanted. "This function must consist of an input filter followed by an amplifier/comparator. When you put in 200 mV pk-pk at 100 kHz, the output must give a TTL signal at 100 kHz. When you put in a 4-V pk-pk signal at 5 MHz, the output must not respond." His intention was to specify a steep roll-off of the frequency response, but he never really said that. He just specified a couple of tests that a good part ought to pass.
The Marketing Engineer at Company B looked at this specification and figured out, "If I put a 200-mV clipper or limiter on the input stage, I can meet that spec with a simple 2-pole roll-off." Sure enough, this approach gave a very simple and low-cost circuit. Company B won the bidding with a low price that many would consider a low-ball bid. They began production and had no problem meeting the incoming inspection tests. But when these signal conditioners were put into service, some worked well. Others, though, worked very badly if they happened to be in a noisy environment (which was the whole reason behind having a filter anyhow).
After some side-by-side comparisons, the circuit with the limiter was found to perform quite differently from the intention of Company A. The filter circuit passed the specified tests and fulfilled the spec. But it failed to meet the intention of Company A, because they never spelled out what they really wanted. They really wanted to be able to put in BOTH the 5-MHz noise and the 100-kHz signal and get a 100-kHz TTL output, while rejecting the 5-MHz noises. The circuit from Company B passed all of the specified tests, but it did not meet this unwritten spec. So, most users found that circuit unusable, and the business fell apart, eventhough the units met every spec. But, YOU would never get caught making that kind of mistake. Would you?
All for now./Comments invited! RAP/Robert A. Pease/Engineer
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