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[OT] It all began with them...



#16

Hello,

Although we're all here for HP calcs, I thought some of you may be interested in seeing the other side of my humble collection: slide rules.

This section still has to get some text since it's now only a list of the slide rules I own with specs but no history, no interesting text.

Thanks for your feedback, if you've got time to cruise on it.

Cheers,
Olivier (_from_Paris)


#17

Olivier,

Slide rules are analog devices since they are always giving you all kinds of results--you pick which one you want. Calculators are digital devices. The two types are very different in many ways (accuracy, ability to chain calculations, memory, programmability).

I feel slide rules and calculators are as different as water and oil.

I used slide rules in high school and college. I also used scientific calculators in college. I was the only student on the engineering campus of Baghdad University who had a programmable HP calculator (at least until I graduated).

Namir


#18

Quote:
I feel slide rules and calculators are as different as water and oil.

You make a good case for the difference between slide rules and calculators, Namir, but there is one similarity you may have missed. Both tools were used for the same purposes. The HP-35 made the slide rule obsolete. It was a better tool, but that just underlines the similarity. The HP-35 was specifically designed to do the same jobs a slide rule did. The fact that it did so faster, with better accuracy and precision, and was easier to boot, are all differences in quality, not in kind. Later, when the programmable hand held calculator came along, you started into territory no slide rule could go. At that point, the distinction becomes clearer, in my mind.

Regards,
Howard


#19

I switched from a slide rule to an HP-45 in college and never looked back.

However, one thing that is very deceptive with a calculator is it can give you a false sense of precision. In most real world applications measurements are only known to two or three digits. For example, if I drive 110 km in 3.2 hours, my average speed would properly be stated as 34 km/hr, not 34.375 km/hr.


#20

Are "significant digits" more apparent when using a slide rule? Or is it just that all those digits are there on the calculator, whether they are significant or not, whereas with a slide rule you have to continue manipulating to get successive digits?

Regards,
Howard


#21

While I don't collect slide rules, I do still have my original Post Log-Log slide rule I used in high school and college. I keep it out so that I am reminded of it and it's just fun to pick up and play with.

Several years ago I read an article about how the change from the slide rule to the calculator/computer has resulted in the loss of the ability to make accurate back of envelope estimates. Especially when dealing with orders of magnitude. Slide rules required you to normalize numbers and to know where you need to place the decimal point in the results. Fascinating article. I've observed this tenancy in some of the young engineers at work. They will believe the answers from the calculator or computer even when, with just a quick rough calculation, it can be shown that the results are way off base.

Bill


#22

Bill,

"Know Your Data" is a good motto to apply. The calculator, computer, slide rule, and so on are just tools that can (under whatever input and processing conditions) give wrong answers. So a person should have an idea of what the results are. If not, double checking the calculations is always a good idea.

I work with statistics a lot, and "Know Your Data" is a good concept to observe, because all these regression tools are not thinking for me, they are just crunching whatever input I give them.

Namir

#23

I'd say a pocket slide rule has about the same accuracy as most physical values you come across: two digits and a reasonable guess at a third.

#24

Quote:
I switched from a slide rule to an HP-45 in college and never looked back.

However, one thing that is very deceptive with a calculator is it can give you a false sense of precision. In most real world applications measurements are only known to two or three digits. For example, if I drive 110 km in 3.2 hours, my average speed would properly be stated as 34 km/hr, not 34.375 km/hr.


From my experience a lot of engineers, back then as well as now, either don't pay attention to precision or forgot how important this is. With a slide rule you only calculate results to a limited precision. The HP-35 gave many more digits of accuracy.

HP must have realized this to be a problem. On the HP-45 they limited the precision at boot to 2 digits past the decimal point. One had to manually change the precision to something greater. I believe they did this through all of the Classics.

-- Dan

#25

Quote:


The HP-35 was specifically designed to do the same jobs a slide rule did. The fact that it did so faster, with better accuracy and precision, and was easier to boot,

Regards,
Howard


Booting the HP-35 was a fairly complex process actually. When turned on, the surge of current starts an oscillation in a DC-DC converter, and charges several capacitors to smooth out 3 different internal voltages. As those ramp up and become stable, a one-shot Schmitt trigger fires which turns on the Sync pulse - a synchronization heartbeat if you will, and resets memory. With Control & timing active the other IC's begin operations and the display drivers start operating.

;)

-- Dan


#26

Dan,

What a coincidence!! My old "solar-powered" slide rule did these tasks too!!

:-)

Namir

#27

I almost changed that to "in the bargain," but then I forgot at the last minute. 8)

Regards,
Howard

#28

Namir,

You were on the cusp of the cutting edge. We oldtimers did not view the sliderule as water viz-a-viz oil with the new electronic calcs. Our sliderule was a lovely lady, she could be long and slim, short and fat, or even round! And sometimes her answers to questions could be very misleading!

tm

#29

JUST IN CASE there are a few of you who haven't seen this...

Why a slide rule is better than a computer...

http://www.physicsforums.com/archive/index.php/t-106586.html

Ren

dona nobis pacem


#30

From that amusing reference: "9. A Slide Rule doesn't need scheduled hardware maintenance."

Maybe not "scheduled maintenance" but I must have aligned the two sides of the slider on my K&E "Deci-log-trig-trig (etc)" at least once a year, trying to make sure that I could really derive and believe that extra half a digit in my results!


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