Sinn 903 KLASSIK, Manual, Page: 31 / 73

31
First and third scale
The movable rotating bezel forms scale 1. With this scale, the figure 10 can signify the
value 1, 10 and 100 etc., depending on order of magnitude. Further scales are located
towards the centre of the dial. The innermost scale (scale 3) is the minute scale, which
you do not need for calculations. The middle scale is used to change minutes into hours
when calculations have a result of more than 60 minutes (e.g. 90 minutes – 1:30 hours).
Second scale
The counterpart to the movable rotating bezel is the fixed scale 2. This is the scale
meant by the second scale in the following examples. At 60 minutes, the second
scale has an arrow labelled MPH. This arrow forms the reference mark for all speed
calculations. In addition, the second scale features red markings at the values 10, 33,
36 and 38. For further information about this, please see the following pages, as well
as for more information about the red markings at the values 10, 36 and 60 on the
scale on the rotating bezel.
Metric scales and logarithmic scales
Scale 1 and scale 2 correspond to scales C and D on the sliderule. That means: you
carry out multiplication, division and rule of three calculations using the disc calculator
based on the same principle as with a sliderule. Whether using the disc calculator or
a sliderule, to carry out calculations you basically need at least two scales. Here’s an
example: when you appose two rules (metric scales, see illustration left) on a sliderule,
you can easily add or subtract two figures (distances). If you use two logarithmic scales
instead of these metric ones, the addition becomes a multiplication and a subtraction
a division.
Important
Like a sliderule, the disc caclulator reflects the numerical sequence of a result. The
established rough calculation (estimation of the order of magnitude of the end result)
is therefore also required without fail here before every operation. The reason: the
number 10 can, for example, mean 1, 10, 100 or even 1,000.