# "A slide rule is a physical instantiation of multiple nomograms:" T or F?

See subject, written in telegraphese. While bouncing around on info from a thread on the Atlantic cable, I came across the gorgeous Smith chart, which needless to say was new to me.

I first was formally introduced to nomograms when I was in a reading-for-the-blind tape recording project, and I can assure you they definitely tested my attention and descriptive ability.

But this idea, the one in quotes, just struck me.

I also thought a clock could be described similarly. But then my examples started to run ahead of what I could define for myself as a correct statement, both in its general validity or how it could be sensibly bounded.

Hence I submit the query to the masses.

Wiki says they are both a “graphical analog computation device”. It’s debatable whether it is more akin to multiple nomograms or one variable nomogram.

A clock doesn’t qualify. It measures or indicates rather than computing.

Small aircraft pilots have long used a flight calculator for computing mileage, flight times, fuel usage, and vectors.

It’s basically a circular slide rule on the front with specific scales useful for a pilot. Turn it over, and the back side is a wind-triangle vector calculator.

ETA: Of course, more modernly, this is done by little electronic pocket calculator devices.

No, in the future they will still use the analog version.

The Wikipedia article on nomograms hints that your subject line is not true:

It doesn’t come out and explicitly say that slide rules are not nomograms, but in comparing/contrasting the two, it implies that one is not a subset or type of the other.

I suppose the OP is correct, but obly technically – a slide rule in a single setting will provide a nomogram for all the possible ways to break down a number into its multipliers. Moving it along will give all the possible multipliers that produce a different product. But it’s still basically one idea and type of calculation (unless you consider the other scales)
I’m fascinated by nomograms. There are entire books and websites devoted to them, and they take a variety of forms and types, and can be used for multiple purposes. That Smith Charet you mentiion, for instance, is mainly used for electrical calculations, but optical thin film designers use it, too, for calculating the transmission of multiple thin films.
What I find most fascinating about nomograms isn’t that they give you a way to calculate without a computer (although they do that, too), but that they give you insight into the way quantities are relatred, giving you an instinctive and intuitive feel for relationships that you don’t get from a calculator, or from the explicit functional form of the relationship. They can often be even better than a graph or plot of the relationship.
As an example, one other thing you can get from a slide rule (although it isn’t what it was made for, as an “instantation of multiple nomograms”) is the relative size of the Benford Probabilities.

Beautiful rule. I like it better in the new configuration.

Very, very smart prop designer.
I’m still thinking about the posts here, but I sense a common trap: citing Wiki as if it has definitive force. It’s just some dude/ette, and silent approval or not caring all that much by a few others, most notably, of course, the more speculative the question is. I’m not disputing them here (but could), nor disagreeing/picking any arguments in this case (although I might) , but this is the SD, after all.

It’s OK. Vulcan vision allows him to read that sucker to 4-5 decimal places, which he then prefaces with “approximately” when relaying the answer to his superior.

And this brings me to the point that slide rules and nomograms teach another valuable lesson: For many applications a fairly crude estimate (+/- 5% say) is perfectly acceptable, and will work just as well as if it had been calculated to within a gnat’s ass. Often as not, at least one of the inputs are not exactly known in the first place, so finding an answer with 3-4 decimal places of precision is just silly.

Could you help out my sorry lazy ass with a few cites? I can see really getting back into this.

I have spent much private and professional time on visual display of information, and it’s time to revisit.

I’d have to look them up. The library when I worked a few jobs back had a couple of books on the topic. Here are a few cites:

http://mathforum.org/library/drmath/view/63338.html

I’ve used the Smith Chart many times for various RF problems. (If I was ever going to get a tattoo…) It’s quite elegant but really nothing more than a complex (the math real & imaginary meaning) impedance chart scaled, normalized and bent such that all values from zero to infinity can be shown.

A picture of my baby from work. (Not mine exactly, but pretty close.)

An interactive Smith Chart (Flash) for anyone who wants to play with it.

I guess all the Mr. Spocks even in the 23rd century still need Jeppesen calculators in outer space to compute their wind triangles!

Solar wind triangles, that is.

Anyone else have trouble writing about nomograms without constantly accidentally typing “monograms”?

[quote=“standingwave, post:11, topic:642552”]

A picture of my baby from work. (Not mine exactly, but pretty close.)…/QUOTE]
Congratulations! But I can never tell if it’s a boy or a girl until the sonograph technician points out the penis.

Also, a nice rear-view traveling down and out the birth canal.

Project Rho’s Antique Instruments page, including several nomogram links:
http://www.projectrho.com/antique.html

Also, from the Atomic Rockets page, Astrogation (slide rules, analog computing, etc.):
http://www.projectrho.com/public_html/rocket/astrodeck.php

ETA: old joke: ask an engineering student how much is two times two, and he’ll pull out a slide rule and after a moment say “About four”.

For sufficiently large values of 2.