The N-1 Law - John Dunn, Consultant, Ambertec, P.E., P.C.

When I was still a young engineer, my boss told me of his absolute belief in "The N-1 Law" which may be stated as follows:

"If for any purpose, a quantity of 'N' items is required, availability shall be limited to a maximum of 'N-1'."

With this tidbit of wisdom once again repeated to me on one particular occasion, he sent me to the company stockroom to obtain exactly six six-lug phenolic terminal strips. Don't come back with five, I was told. Make sure you get six of them. Off I went.

At the stockroom, the clerk took a handful of terminal strips from a large bin and carefully counted them out one by one as they were dropped into a small paper bag. It was plop! (One), plop! (Two), ....... plop! (Six) and back I went with the treasure in hand.

I handed the paper bag to my boss who poured the strips out on the table and then suddenly he threw one of them across the room into the nearest wall, his face reddened with the effort.

Why?? I picked up the thrown terminal strip, looked closely and discovered a hole where one of the strip's terminals was missing.

 

It was incontrovertible proof from on-high that "The N-1 Law" is indeed a fundamental property of this universe.

Thank you, Edsel Murphy.

 

Comments

[John Dunn]

For those who might not know, the Harris' Theorem to which I refer is not that for "asymptotic coupling" or any similar issue but comes instead from QST magazine published by the ARRL and states (paraphrased):

Any dropped tool will always land where it can do the most damage.

[Alex Iwanow]

As a young 1970s engineer, I designed a circuit with several dozen components and was preparing a production run of 100. Since the PCBs were part of a medical device, I had plans to pre-assembly-test 10/1000 of each component, even though I had purchased 100% "vendor pre-tested-burned-in" components. My boss complained the tests we redundant.
I felt great but uneasy. As my boss looked over my shoulder, the very first part failed - a 1N914A diode had reversed marking band! Needless to say I tested all 1000 diodes and still made the deadline delivery that evening.

A lesson learned early that re-occurred several times in my career.

Alex Iwanow

[Michael Alderete]

Hah!! no further comment

[William Ketel]

The unfortunate reality is that testing or measuring will always be required for any process that is not "100% controlled", meaning that checking is needed if there is not 100% certainty that the results will be exactly as desired.
As for the issue with the terminal strips, I would never ever trust any supply area to have every single part both correctly placed and be the correct part for that place. And any assembly that must work the first time must always have all parts checked prior to assembly. That actually is good economics, which is to catch faults before to much value is added.