Scales (Slide Rule): Difference between revisions
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==== Slide Counting ==== | ==== Slide Counting ==== | ||
A peculiar feature of slide rules is the fact that the scales "wrap around" themselves quite often. This leads to a very nice tool in tracking any extra complications with the decimal point: the slide itself. When performing the standard multiplication procedure (starting at an index), any time the upper index is used, this represents using this "wrapping" feature, which in essence describes adding 1 to the characteristic at the end. With division, the operation is reversed, meaning that any time you reach the upper index, you have to subtract one from the characteristic. The actual rule takes more reasoning, but can be described as follows: if multiplying brings you ''down'' the rule, add one to the characteristic (using either method of multiplying). Likewise, if dividing (using either method) brings you ''up'' the rule, subtract one from the characteristic. This can be seen by using our previous example on scientific notation: | A peculiar feature of slide rules is the fact that the scales "wrap around" themselves quite often. This leads to a very nice tool in tracking any extra complications with the decimal point: the slide itself. When performing the standard multiplication procedure (starting at an index), any time the upper index is used, this represents using this "wrapping" feature, which in essence describes adding 1 to the characteristic at the end. With division, the operation is reversed, meaning that any time you reach the upper index, you have to subtract one from the characteristic. The actual rule takes more reasoning, but can be described as follows: if multiplying brings you ''down'' the rule, add one to the characteristic (using either method of multiplying). Likewise, if dividing (using either method) brings you ''up'' the rule, subtract one from the characteristic. This can be seen by using our previous example on scientific notation: | ||
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431 x 0.00085 = (4.31x10²)x(8.5x10⁻⁴) which implies a characteristic of 2 - 4 = -2 | 431 x 0.00085 = (4.31x10²)x(8.5x10⁻⁴) which implies a characteristic of 2 - 4 = -2 | ||
4.31(D) | I → 8.5(C) ≈ 3.67(D), which is lower on the rule than we started (4 > 3), therefore we need to add 1 to the characteristic (-2 + 1 = -1). | 4.31(D) | I → 8.5(C) ≈ 3.67(D), which is lower on the rule than we started (4 > 3), therefore we need to add 1 to the characteristic (-2 + 1 = -1). | ||