Granddad’s Altimeter

One of the most interesting mementos that I have from my grandfather is a surplus mechanical altimeter from the early days of United Airlines. It was an unusual object for a kid to see on someone’s bookshelf — even given that Granddad was a maintenance supervisor for United. I would look at it and wonder what it was and why it was there — until one day I asked him about it.

Granddad's altimeter / barometer. (Click for larger.)

Granddad’s altimeter / barometer. (Click for larger.)

He told me that it was an aircraft altimeter — and that it still worked well, although it hadn’t been calibrated in a long time. Pressure altimeters, such as this one, work by comparing the ambient air pressure to the current theoretical sea level air pressure for a given location (measured by weather stations at airports.) Since air pressure decreases with altitude (at sea level, by about one inch of mercury for every 1000 feet), the difference in air pressure can be used to determine an aircraft’s current pressure altitude. When corrected for local weather-related changes in air pressure, a reasonably good estimate of the aircraft’s actual MSL altitudeĀ can be obtained.

Granddad, as it turned out, was using the altimeter somewhat backwards — as a barometer. Since the altitude where he lived was nearly at sea level, he could set the altimeter’s barometric setting to the standard value of 29.92, and then use it to monitor changes in the local air pressure. If it showed zero altitude — sea level — the local air pressure must be 29.92 inches of mercury. If it read lower, that meant that the air pressure was higher than average, and fair weather could be expected. When it started reading higher than sea level, the air pressure was lower than average, possibly indicating stormy weather.

I found that to be one of many valuable lessons that Granddad taught me over the years I knew him: Just because something wasn’t intended to do something, doesn’t mean it can’t do a perfectly good job.

Besides, it looks a lot cooler than a typical barometer — and makes such a cool, practical,
conversation piece.

Posted in Aviation, Nostalgia, Science | Leave a comment

Ladyada interviews Paul Horowitz

Now here are two celebrities actually worth watching. Limor “Ladyada” Fried, electronics geek extraordinaire and founder of Adafruit Industries, interviews Paul Horowitz (of Horowitz and Hill fame)! (Limor’s apparently interviewing Hill on the next one.)

Included at 3:15 is a shocking revelation:
Paul Horowitz never took an electronics course!!

Now — invite Hill, Jeri Ellsworth, and Steve Wozniak, and let’s really get this party going!

Posted in Analog, Current Events, Digital, Electronics, Resources | Leave a comment

Third Edition

The Book Is Retired. Long Live The Book!

Earlier this month, Electronics geeks around the world felt a disturbance in the Force. A presence they had not felt since 1989. This disturbance, however, was most welcome. The long-rumored Third Edition of The Book was actually here.

“The Book,” of course refers to H&H. The Bible. TAoE. The Good Book.
The Art of Electronics, by Horowitz and Hill.

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TAoE is technically a textbook, but finds its best use as a reference.


It’s a testament to how well-written and comprehensive TAoE is, that a quarter century after the second edition was published, it was, in many geeks’ minds, stillĀ the book on electronic circuits. Now, finally, H&H have updated the book, incorporating many new modern topics. The fundamentals haven’t changed since 1989, but digital electronics certainly has.

If you’re into electronics and don’t have one, go get one. It’s worth it.

Posted in Analog, Current Events, Design, Digital, Electronics, Fundamentals, HOW-TO, Nostalgia, Resources, Reviews, Troubleshooting | Leave a comment


Explore the galaxy! See fascinating sights! Meet interesting people, some of whom may not, in fact, actually start shooting at you right away!

My trusty Hauler, outfitted for exploration, docked at Pratchett’s Disc. (Click for larger.)

Cynicism aside (although, to be fair, the inhabited part of the in-game universe is a rather bad neighborhood), Elite:Dangerous is a fun way to explore the galaxy. As you would expect from a title in the Elite series, it is set in the actual Milky Way galaxy. Stars are, at least to a reasonable extent given our imperfect knowledge of them, in the correct places and of the correct classes. Space stations (along with the FTL drive, still science fiction) are actual, working places that you can navigate to, dock inside or on, and interact with. The larger ones even rotate, simulating gravity.

The entire galaxy is rendered at its actual size of about 100,000 light-years across, meaning that even with the futuristic FTL “frame shift drive” that ships employ, getting across the galaxy can take quite some time. A Hauler outfitted similarly to mine, for instance, can jump about 30LY at a time, if there is a suitable star nearby to jump to. Given optimal placement of stars, this means that a trip to the center of the galaxy would take about a thousand jumps, give or take.

Fastest paths to all star systems within 100ly of my current location. (Click for larger.)

Fastest paths to all star systems within 100ly of my current location. (Click for larger.)

Zoomed out, 100ly no longer looks quite as large. (Click for larger.)

Jumping directly from one system to the next without stopping except to refuel seems to take about 45-50 seconds per system, at least in the Hauler I’m currently flying. So a trip to Sagittarius A* (which, of course, exists in-game) will take at least twelve hours or so. An Anaconda — a huge almost-capital-ship which I can’t yet afford — is said to be able to do 38ly at a jump, which should cut that down to 9-10 hours or so.

At this scale, the 100ly sphere of routes is barely even visible at all. (Click for larger.)

At this scale, the 100ly sphere of routes is barely even visible at all. (Click for larger.)


Modern technology is fun: I visited the Orion Nebula yesterday. How was your weekend?

Posted in Games, Toys | Leave a comment