Electronic Design

Bob's Mailbox

Dear Bob:
In your April 20 column, you mentioned that someone corrected your use of the red thermocouple wire as the positive lead. Actually, there is no "correct" answer.

It seems that the IEC standard for thermocouple color coding calls out red as the plus lead; this standard is used around the world, except in the U.S. The U.S. uses an ISA/ANSI standard for thermocouples that calls out red for the minus lead.

This standard has expired, and there is a big controversy going on (or at least there was a few months ago) over whether or not to adopt the IEC standard in the U.S. (This would cause quite the confusion, what with the huge installed base of minus red lead thermocouples already in place.) You can search for more info about this on the web.
DEAN ATHANIS
Another ex-Philbrickian,
via e-mail

P.S. I got five minutes for the bridge crossing puzzle, too—although I bet Ari would've slowed down a bit by the time he carried the third guy across!

Thanks for clarifying "which way is up!" Maybe they'd better pick some new colors—not red or yellow. And hey, that ARI is a tough guy! (One guy suggested they could get over in 12 minutes if they just waited 'til morning.)—RAP

Dear Bob:
Re: manhole covers (Puzzler #7, in the April 6 issue): I knew why they were round. In Minnesota we had rectangular storm drain covers, which some kids would often drop into the sewers below. But not having been in Nashua very often (I did live in Lynn, Mass.), I failed to notice the triangular manhole covers up there.

I immediately thought of a large pressure vessel, such as a boiler or locomotive inspection cover. This type of "Manhole" is big enough for some hapless boilerworker (boilerperson doesn't sound right) to crawl inside. The cover has a ledge on the inside to withstand the high pressure, and is merely held in place from the outside by a set of "dogs" or other clamping device. The manhole is oval, to permit it from being unbolted. And when the pressure is relieved, it may be lifted into the vessel, twisted 90 degrees twice, and withdrawn from the pressure vessel. Does this count as a non-round "manhole?"
ROBERT DAHLGREN
Fujikura Technology America Corp.
via e-mail

Hello, Robert D. On the FRONT of a steam locomotive, you will often see a large round Disc, the inspection hole for the Steam Box—fastened down by bolts or dogs. Those discs are round, usually. Perhaps three or five feet in diameter. But THEY do not have to hold any particular pressure, maybe three or seven pounds per square inch. They are just fastened on the outside of the engine, on the front.

The manholes YOU refer to DO have to stand off a whole lot of pressure. You are correct that oval is a very good shape for them, and that they get turned and turned and mounted inside.

In some cases, where there is not a lot of stress, a single bolt & (two-eared) clamp holds them in place. I can't guess how many years ago that was figured out, but maybe 200 or 300? Maybe more? I'll try to check into this. Your point is nicely taken.—RAP

Hi Bob:
I always enjoy your Pease Porridge. In regard to the April 20 column, you mentioned getting a "whack" for spilling your milk as a kid. Well, as recent parents, we give our son "swats" for being bad. We don't punish accidents, but deliberate misbehavior is another matter. (I tend to agree with your policy. Of course, there is every kind of INTERPRETATION..../rap)

We have an excellent example of what not to follow living across the street. On one occasion, we observed the younger boy taking a roundhouse swing of a hollow plastic bat and connecting (squarely, I might add) with the back of his older sister's head. Repercussions, you might ask? Their mother ordered the boy to apologize to his sister and give her a hug. (One of these days, he may use a wooden baseball bat, not realizing what damage can thus be caused...not just repercussions, but CONcussions—or death. Sigh. /rap)

This is but one of a forest of stories about these kids and their parents. By not controlling and punishing this behavior, the parents encourage them to use similar tactics on others (and it has happened).

So, the question to ask the reader who claimed you were "brutal" to your son is: Who is more "brutal?" The parents who allow their children to misbehave, so as to not damage their delicate psyches—yet the children grow up to be reckless and irresponsible adults? Or, the parents who risk hurting their children's feelings when they misbehave so that they grow up to be responsible and respectful adults? (A very well-phrased question.../rap) I happen to believe that you did the right thing.
Bob Becker
via e-mail

IF my son had pulled the glass away, I think I would have given him a very SMALL swat—just to get his attention, maybe a rough pat on the shoulder, so he would realize he had made a mistake.

I know a gal who always threatened her kids, "If you don't start behaving right away, I'm going to beat your a** 'til your nose bleeds." But she never did. And I think one of her kids grew up OK. The other one I'm not so sure about, and the third is in the PEN, doing 5 to 10....

Sigh...one out of three is not a great batting average....—RAP

All for now. / Comments invited!
RAP / Robert A. Pease / Engineer
[email protected] team.nsc.com—or:

Mail Stop D2597A
National Semiconductor
P.O. Box 58090
Santa Clara, CA 95052-8090

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