Precision Rules
Cylindrical Slide Rule.
When I was about fourteen I remember my maths master bringing in the first electronic calculator I had ever seen. It could do addition, multiplication, division and subtraction and had one memory. It cost around £300 in today’s money. By the end of my undergraduate studies I had a programmable scientific calculator that handled trig functions and statistics and cost only £30.
In the sixth form (i.e. years 12 & 13) we used slide rules and books of tables for calculation as calculators weren’t generally allowed in examinations. The slide rule I had was an advanced one, double-sided with trigonometric, log and exponential functions built in.
In many ways slide rules remain superior to calculators. They are fast, intuitive and less prone to errors of data entry. In experienced hands fairly complicated calculations can be done rapidly. They also make it easier to estimate answers and they teach you to handle the powers of ten in a calculation so that they become second nature. These skills become very important at university in a complex subject like Physics as you need to work out whether you are on the right track quickly when you are working a problem.
All slide rules work on the same principle. You can save doing a multiplication of two numbers by converting the numbers to their logarithms and then adding those together, finally converting back to ordinary numbers. In this way a multiplication becomes a simple addition which is way easier. Slide rules work by converting the log numbers into lengths on the rule and by sliding one bit of rule against another you can add the lengths (literally) and then read back the total length to convert back to the normal numbers.
The main drawback with slide rules is precision. An ordinary slide rule can work to about three significant digits whereas calculators work at eight or more. Of course precision doesn’t buy you much if you have entered the wrong figures into the calculator in the first place.
The precision is determined by the length of the slide rule: they’re normally about a foot long. Any longer and you have problems getting them in your briefcase :)
This is an image of my father’s precision slide rule. It gets around the length problem by spiralling the scale around a cylinder. The cylinder is in three parts that can rotate independently the scales on the top and bottom parts with a sliding sleeve in between. Collapsed down it is about six inches long, but the scale is equivalent to a slide rule about five and a half feet in length!
This is a picture of the top scale and part of the central sleeve, on top of some of the instructions for the device (an Otis King model “L” if you are a detailophile :) ).
I created this for the Macro Mondays Back In The Day theme this week. The exposed area of the scale is 1.3 inches so we are within the limits for the group - yey! Also for 7DWF :)
Thank you for taking time to look. I hope you enjoy the image! Happy Macro Mondays!!
[Indoors with light from window; tripod mount; remote release; focused in LiveView; VR off.
Processed in Lightroom with the colour balance set to accentuate the brown tinge in the instructions paper; exposure and contrast set to create a bit of ambience; rotated to give a stronger diagonal, and cropped.
Into Affinity Photo for some healing of dust spots; sharpened with a bit of Clarity filter and Unsharp Mask; slight, carefully constructed vignette to keep the highlights on the knurling top right, but to draw us in a bit. Then we’re done :)]
Precision Rules
Cylindrical Slide Rule.
When I was about fourteen I remember my maths master bringing in the first electronic calculator I had ever seen. It could do addition, multiplication, division and subtraction and had one memory. It cost around £300 in today’s money. By the end of my undergraduate studies I had a programmable scientific calculator that handled trig functions and statistics and cost only £30.
In the sixth form (i.e. years 12 & 13) we used slide rules and books of tables for calculation as calculators weren’t generally allowed in examinations. The slide rule I had was an advanced one, double-sided with trigonometric, log and exponential functions built in.
In many ways slide rules remain superior to calculators. They are fast, intuitive and less prone to errors of data entry. In experienced hands fairly complicated calculations can be done rapidly. They also make it easier to estimate answers and they teach you to handle the powers of ten in a calculation so that they become second nature. These skills become very important at university in a complex subject like Physics as you need to work out whether you are on the right track quickly when you are working a problem.
All slide rules work on the same principle. You can save doing a multiplication of two numbers by converting the numbers to their logarithms and then adding those together, finally converting back to ordinary numbers. In this way a multiplication becomes a simple addition which is way easier. Slide rules work by converting the log numbers into lengths on the rule and by sliding one bit of rule against another you can add the lengths (literally) and then read back the total length to convert back to the normal numbers.
The main drawback with slide rules is precision. An ordinary slide rule can work to about three significant digits whereas calculators work at eight or more. Of course precision doesn’t buy you much if you have entered the wrong figures into the calculator in the first place.
The precision is determined by the length of the slide rule: they’re normally about a foot long. Any longer and you have problems getting them in your briefcase :)
This is an image of my father’s precision slide rule. It gets around the length problem by spiralling the scale around a cylinder. The cylinder is in three parts that can rotate independently the scales on the top and bottom parts with a sliding sleeve in between. Collapsed down it is about six inches long, but the scale is equivalent to a slide rule about five and a half feet in length!
This is a picture of the top scale and part of the central sleeve, on top of some of the instructions for the device (an Otis King model “L” if you are a detailophile :) ).
I created this for the Macro Mondays Back In The Day theme this week. The exposed area of the scale is 1.3 inches so we are within the limits for the group - yey! Also for 7DWF :)
Thank you for taking time to look. I hope you enjoy the image! Happy Macro Mondays!!
[Indoors with light from window; tripod mount; remote release; focused in LiveView; VR off.
Processed in Lightroom with the colour balance set to accentuate the brown tinge in the instructions paper; exposure and contrast set to create a bit of ambience; rotated to give a stronger diagonal, and cropped.
Into Affinity Photo for some healing of dust spots; sharpened with a bit of Clarity filter and Unsharp Mask; slight, carefully constructed vignette to keep the highlights on the knurling top right, but to draw us in a bit. Then we’re done :)]