Electronic Design

Bob's Mailbox

Dear Bob:

I am replying to your invitation to comment on test specs. Once upon a time in a previous "incarnation," I worked at a major defense contractor on an electronic system. Most of the system was made up of modular components purchased from suppliers. As a consequence, the system performance was highly dependent upon supplier performance. Also, we used multiple vendors to reduce cost.

We specified absolute minimum parameters (easier for the incoming guys). There were some very interesting variations in the parameters from vendor to vendor. We used one vendor (Watkins-Johnson) extensively in prototype design. Their parts usually showed a normal Bell curve with the 3-sigma point at about the low spec limit. Of course there was a fair variation of actual performance with most units moderately to significantly better than spec.

When we bought other vendor's parts, the distributions were quite different. A few failed outright. A couple of amplifier vendors and one filter vendor made parts that were RIGHT at the low spec limit. Subsystems that passed easily with prototype parts failed with the new parts. The moral of the story----don't assume normal distribution from vendors until you have a track record.

Most of us can't afford Rolls Royces. Most of our customers can't either. Therefore, acceptable quality is an issue that must be managed constantly. (Tests cost money, too.)



Chicago, Ill.

When you buy components, you either have to be able to use anything that is in spec, or, you have to talk to the supplier and understand what their distributions will be like.----RAP

Dear Mr. Pease:

I have read your columns for many a year and have particularly enjoyed your expose of Fuzzy Logic. I write control logic for traffic controllers and can see little or no benefit in so-called Fuzzy Logic! You are to be commended for taking on the establishment on this subject.

This letter is written, however, to congratulate you on the message conveyed in your article on JIT. I have wondered for years how any manufacturing entity could benefit by having someone else stock parts for crucial production requirements. As you point out, one way or another, someone has to pay for the inventorying of critical parts.

This reminds me of the financial gurus that claim it's cheaper to lease a car than to purchase. I learned long ago that most business leases are to circumvent rules or laws, or to obtain a cheap car for personal use after the company's inflated lease expires. Of course, there may be genuine reasons like poor credit or inability to borrow that would favor leasing in lieu of purchasing, but they do not make it cheaper.

Finally, I have collected articles for years about fantastic claims and inventions including leasing. You mentioned this area a few issues ago, and I agree that this is a subject that needs some airing. Perhaps I could provide some good examples for your future column.


Gammatronix Inc.

Dublin, Ohio.

If leasing were cheaper than buying, then the guy who leases you a car would be losing money....eh?----RAP

Dear Mr. Pease:

I am responding to your "What's All This Apples And Oranges Stuff, Anyhow?" column. My comments are as follows. YOU HIT THE NAIL ON THE HEAD! I have experienced the arena you discussed in your "Training Course" and you get the Don Quixote award for "tilting at windmills."

My experience as a production supervisor in several small OEMs over the past 16 years has been similar, from the JIT stuff, to the ROI and Quality lectures. There are several conclusions I have drawn that I wish to share with you.

First, I do agree with you on anticipating our customers' ordering patterns and being proactive on that front. The lack of product projections from the "executive sales force" has resulted in my finally obtaining a computer a year ago, and logging with spreadsheets and my own formulas, a manufacturing schedule.

These projections are critical to control inventory flow, manpower scheduling, etc. The executive group is empowered to drive that, yet always seem reluctant. I also believe in the GOOD, FAST, and CHEAP----pick 2, mentality. I always opt for GOOD and FAST. Cheap always causes problems in an initial prototype and pilot job, and profitability can always be improved once the roll-out begins. Product improvement is another subject that needs financial support in a manufacturing environment.

As far as purchasing goes, and only taking orders from those who order well in advance of delivery, that would be impossible unless you were the only one who could do the job. If you wish to capture the market share, you HAVE to offer better performance, quality, and customer satisfaction. Ultimately, and in conclusion, I believe that you need well-trained employees who are instilled with a caring attitude created by a strong code of ethics exhibited and driven from the top. This will result in creating the only choice for the customer.

It is indeed unfortunate that these type of lectures run rampant in the industry, and that people actually pay a lot of money to attend them. It makes you think of the saying, "those who can't, teach." Teachers are to build foundations and to free your imagination to be able to think, not confine you with a set of surrealistic rules that flow down the narrow path to nowhere. The bright spot in all this is that these people do exist and they are the few who are making the right moves. Thank you for being one of them.


Production Supervisor

Datatec Industries

Fairfield, N.J.

Thanks for the sanity check. Education beats training, and we have to let our people think and ask questions, when they suspect the training is giving wrong answers.----RAP

Dear Bob:

Halleluya! At last...someone is starting to talk sense about electric cars. I agree with everything you said in your Aug. 8 column, but would like to point out something that everybody who is in favor of electric cars seems to forget.

Electricity does not happen by accident. It's generated by usually fossil- fuel-burning power plants, they have been known, on occasions, to emit some polluting waste. If we would substitute all of the gas burned by millions of cars, the increased emissions from the power plants may well overwhelm us, to say nothing of the cabling to make sure every house has the ability to charge one, or two, or three car batteries overnight. Every night!

What also seems to escape discussion is the effect of the conversion efficiencies involved in the process of turning coal or oil into volts and amps. I believe, but have not calculated, that the losses in this train would more than offset any gain in efficiency by burning all the fuel in one place (the power plant), and distributing it everywhere else.


European Sales Manager

Dallas Semiconductor Corp.

Birmingham, England

Coal-burning power plants average 36% efficiency. An efficient car rarely beats 30% peak efficiency, and 12% average. Even after battery-charging losses, they'll beat the gasoline engine. ----RAP

All for now. / Comments invited!  RAP / Robert A. Pease / Engineer


Mail Stop D2597A

National Semiconductor

P.O. Box 58090

Santa Clara, CA 95052-8090


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