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FX Series Programmable Controllers Devices in Detail 4
4-43
4.15 Floating Point And Scientific Notation
PLC’s can use many different systems and methods to store data.
The most common have already been discussed in previous sections e.g. BCD, Binary,
Decimal, Hex. These are what is known as ‘integer’ formats or ‘whole number formats’.
As the titles suggest these formats use only whole numbers with no representation of fractional
parts. However, there are two further formats which are becoming increasingly important and
they are:
a) Floating point and
b) Scientific notation
Both of these formats are in fact closely related. They both lend themselves to creating very
large or very small numbers which can describe both whole and fractional components.
General note:
• Sometimes the words ‘Format’, ‘Mode’ and ‘Notation’ are interchanged when descrip-
tions of these numerical processes are made. However, all of these words are providing
the same descriptive value and as such users should be aware of their existence.
Some useful constants
π 3.141 ✕ 10
0
2π 6.283 ✕ 10
0
π/4 7.853 ✕ 10
-1
π
2
9.869 ✕ 10
0
The speed of light 2.997 ✕ 10
8
m/s
Gravity, g 9.807 ✕ 10
0
m/s
2
e 2.718 ✕ 10
0
Fixed points:
Boiling point of liquid oxygen -1.8297 ✕ 10
2
°C
Melting point of ice 0.00 ✕ 10
0
°C
Triple point of water 1.00 ✕ 10
-2
°C
Boiling point of water 1.00 ✕ 10
2
°C