Slide rules... - Page 1
Forum section: electronics / general

author: ampdoctor
author_rank: Frequent Contributor
timestamp: October 12, 2013, 03:11:45 pm
content: Every now and again the thought about acquiring a slide rule or two flies through my head. Then I realize I've got no idea how to even use one. I remember our high school math classrooms had a giant mock up hanging on the wall, presumably to teach you how to use them, but by the early 80's they had already been effectively phased out of general usage.After having a quick look around, there seems to be a rather large variety of types and configurations for different purposes. So I thought I'd post this up and see how many people here actually have experience working with these relics and what type might be most useful to play around with...just for shits and grins.

author: SLJ
author_rank: Frequent Contributor
timestamp: October 12, 2013, 03:58:10 pm
content: Here's one in my collection. We had to use slide rules in my first electronics classes as digital calculators were new and still out of our price range in the late 1960s and early 70s.It's made specifically for electronics use. This slide rule was distributed by the Cleveland Institute of Electronics. It has a typical math slide rule on one side with electronics calculations and electronics formulas on the other.I have others in my collection, mostly electronics based cardboard slide charts and wheel charts. Some go back to the 1920s:http://www.stevenjohnson.com/cardboard/index.html

author: JackOfVA
author_rank: Unknown
timestamp: October 12, 2013, 06:10:07 pm
content: I completed my EE degree before electronic calculators, so it was all slide rule work. Have a 10" K+E plastic faced mahogany slide rule that I carried for 4 years and my backup -- a 5" K+E plastic pocket rule.Much prefer the mahogany rules, but you have to keep them lubricated with a pinch of talcum powder every now and then.

author: rolycat
author_rank: Super Contributor
timestamp: October 12, 2013, 06:26:37 pm
content: This [Made in England] slide rule sits ready for action in my desk, although this is the first time it's been used in maybe thirty years:This is a close-up showing that 12 (on the D scale, aligned with the left hand end of the C scale) x 195 (on the C scale) = 2340 (read off the D scale):Placing the decimal point is your responsibility.It was already obsolete when I acquired it in the late 1970's, but school rules at the time forbade calculators in the classroom, so I couldn't use this splendid example of the white heat of [Made in Japan] technology:This dates from 1975 and still works perfectly. It uses a VFD and emits a rather charming high-pitched whine when in use. It's about 29mm thick and weighs around 200g (1.1 inches and 7 ounces for the metrically challenged). Powered from 4 AA cells.In dim light one can see two red-hot cathode filaments running across the display and contributing to the 0.4W power consumption proudly displayed on the back of the calculator.

author: saturation
author_rank: Super Contributor
timestamp: October 12, 2013, 07:03:18 pm
content: I was in the last class to use a slide rule and trig/log tables. It was a full course, so to use the calculator meant eliminate the class from the curricula. My first scientific calculator was also the fx102; I remember it fondly because it had softer keys than most Casios, a crisp display, fast response, and it was stolenI do recall it was a battery hog by today's comparison; my College fx 100 still sits in my work desk today with itsoriginal30+ year old CasioAAbatteries

author: netdudeuk
author_rank: Frequent Contributor
timestamp: October 12, 2013, 10:17:48 pm
content: I've still got my FX-31 in my desk drawer. It's very similar to the one above and includes the fractions and degrees, minutes, seconds display which were not that common at the time.

author: netdudeuk
author_rank: Frequent Contributor
timestamp: October 12, 2013, 10:18:53 pm
content: I should add that seeing those slide rules made me shudder. I had my own in about 1975.

author: denneyaa
author_rank: Unknown
timestamp: October 12, 2013, 10:19:16 pm
content: I actually had gotten a couple of these from my uncle as a Christmas gift when I was in high school and thinking about going into architecture. He spent the whole day teaching me how to use them and the concept of how they worked. After that day I only really remember a little about how to use them, but when the batteries run out in my calculator, I remind myself that I'm lucky to be able to have the technology of it, even if some people can be faster on the slide rule.

author: Jon Chandler
author_rank: Frequent Contributor
timestamp: October 12, 2013, 10:46:40 pm
content: A nice thing about slide rules is that they force you to think about significant digits. For example, if you measure to nearest tenth of a millimeter, the eight or more digits a calculator gives you when converting to inches are meaningless.

author: ampdoctor
author_rank: Frequent Contributor
timestamp: October 13, 2013, 02:28:56 am
content: It seems one of the disadvantages of slide rules is that you need a bit of an understanding of arithmetic and estimation skills to make them work. How dare they! LOLOne of my physics prof's gave a little speech one time on the toxicity of calculators when somebody started grousing about not being allowed to use anything resembling programmable or graphing calculators on exams. I think he said he could get 3 sometimes 4 significant figures with a slide rule if it's high enough quality.He also swore he could outrun a calculator any day of the week with his head, a slide, and a pencil and paper.Some days I wonder if for all the gains we've made in technology, we've also managed to throw the baby out with the bath water.

author: rarthur22
author_rank: Newbie
timestamp: October 13, 2013, 05:07:40 am
content: I remember having a brief lesson on slide rules in high school in the early 80's. However calculators were in style and getting rather inexpensive. Has Dave done any video's on how to use a slide rule? I have watched quite a few of his videos and haven't heard him mention them at all.

author: IanB
author_rank: Super Contributor
timestamp: October 13, 2013, 05:23:47 am
content: Quote from: rarthur22 on October 13, 2013, 05:07:40 amSlide rule videos have been done on other YouTube channels, for instance by singingbanana. On a related note you can find a video about log tables on Numberphile.

author: vk6zgo
author_rank: Super Contributor
timestamp: October 13, 2013, 07:08:05 am
content: I knew the principles of slide rules,but never quite got the "knack" of using them.I used pencil,paper,& log tables,until calculators became affordable.Programmable calculators were banned from exams for a while.I couldn't see a lot of point programming tons of crud on your calculator,when most of the time you only needed the normal functions & knowledge of your subject.

author: SeanB
author_rank: Super Contributor
timestamp: October 13, 2013, 07:49:16 am
content: Dave is in the calculator era. I used log tables, scratchpad multiply and addition and long division at school. Only in the last year did they start to introduce a calculator. I still have my dad's old calculator that I used in school, a Casio FX602P, and it still works fine. Nice thing is while it was a programmable it was not seen as such, as the teachers had a simple rule to see if it was a programmable unit by looking on the back to see if there was an all reset button there that cleared all data inside. But then again internal memory was 512 steps, not going to fit much in there.With the FX102 whining you need to go inside and change the 2/3 small electrolytics in the power supply and it will stop whining. These tend to dry out over time, and new ones are easy to fit in place of them.

author: G7PSK
author_rank: Super Contributor
timestamp: October 13, 2013, 08:55:19 am
content: When I was at school there were no affordable electronic calculators and they were not allowed in exams period. We had to use slide rules and log tables (solid oak) the school did provide some calculators in the maths class room large grey machines with a silver crank handle at one end and dozens of silver dial wheels with red numbers on them, these would break your foot if they got dropped.

author: geo_leeman
author_rank: Regular Contributor
timestamp: October 13, 2013, 01:25:15 pm
content: I have my father's slide rule. When he was in college as a geologist in the mid 1960's he ended up with a Pickett "Trainer" slide rule. Every now and then I get the notion to pull it out and use it on the bench for fun. Though it is a basic slide rule the instructions that came with it were very thorough! Should you want to do multiplication/division you can also use two rulers with metric scales. Same principle.

author: Dr. Frank
author_rank: Super Contributor
timestamp: October 13, 2013, 01:43:04 pm
content: I've still got mine, 30 cm long, from about 1976.We used them quite a lot, even in tests. And I still know how to use it.One year later, our school bought a suitcase full of TI pocket calculators.Then, the religious calculator war between us pupils began, i.e. whether you were a HP or TI follower.I got a TI 58, which worked until university.Frank

author: rolycat
author_rank: Super Contributor
timestamp: October 13, 2013, 01:52:14 pm
content: Quote from: geo_leeman on October 13, 2013, 01:25:15 pmNo, you can't. With two rulers all you can do is add and subtract.And metric scales are not required; any units will do as long as they have a constant increment.

author: geo_leeman
author_rank: Regular Contributor
timestamp: October 13, 2013, 02:09:15 pm
content: Quote from: rolycat on October 13, 2013, 01:52:14 pmDOH!It's early in the morning here! Thanks for the correction.My father said there were semester classes in using these things whilst he was in school. I'm currently a PhD student (Geophysics) and try to avoid calculator dependence, but it's sure getting hard with wonderful tools like Wolfram Alpha.

author: Dr. Frank
author_rank: Super Contributor
timestamp: October 13, 2013, 02:23:29 pm
content: Quote from: geo_leeman on October 13, 2013, 01:25:15 pmWell, has nothing to do with metric or imperial system!The scales on slide rulers were logarithmic or double logarithmic, so you can only do multiplication, division, logarithm, but no addition or subtraction.On mine, there were also some other tables engraved, for sine, cosine, inverse and exponential function.Frank

author: rolycat
author_rank: Super Contributor
timestamp: October 13, 2013, 03:03:26 pm
content: Quote from: Dr. Frank on October 13, 2013, 02:23:29 pmIn order to actually obtain logarithms you also need a linear scale on your slide rule, typically labelled L. If you had one of these on the slide as well as the body it could be used for addition and subtraction.Curiously enough there were actually a few slide rules which let you do this. Two of these were made by Pickett, the American company who manufactured geo_leeman's father's instrument.One would have thought that anyone smart enough to use a slide rule could also add or subtract two numbers, but Americans are strange creatures...

author: magiccow
author_rank: Contributor
timestamp: October 13, 2013, 03:53:58 pm
content: I've got a couple of slide rules: one about 20cm long that I actually used in exams in the late 70's and a nice pocket rule I bought in an antique shop a short while ago. It was marked "ruler" - obviously no-one knew what it was.Certainly calculators are a lot more convenient now, but slide rules were good because you had to place the decimal point yourself (so you had to estimate the magnitude in your head) and (as noted by earlier commenters) the precision is limited to a couple of significant figures.I don't use the slide rules now (in fact I don't do that many calculations now), but they're beautiful things and I love them.

author: geo_leeman
author_rank: Regular Contributor
timestamp: October 13, 2013, 04:22:12 pm
content: Quote from: magiccow on October 13, 2013, 03:53:58 pmThey are.. and every now and then it's nice to play with them!While yes, you can use the imperial system to do the addition/subtraction on a ruler, I just mentioned metric as it's much easier to read off than the oddly spaced imperial marks.I've seen several companies that made multi-sided rules and then very large (on the order of several feet) demonstration rulers for instructors to used in the classroom. Those are relatively collectable - and would make a great conversation piece.http://www.1stdibs.com/furniture/more-furniture-collectibles/scientific-instruments/pickett-slide-rule-4-foot-model-teacher-classroom-demonstration/id-f_773168/

author: silent
author_rank: Contributor
timestamp: October 14, 2013, 10:45:11 pm
content: I have been growing in the calculator era, but I still have one (same as the one on the picture below) which my father was using on his studies in early 80s. In Poland it was called like "logarythmic slider" - due to log scale.By the way, it's a pretty solid polish piece of plastic crap - it's still fully usable after over 30 years and looks like almost new one ;-).