FX Series Programmable Controllers Devices in Detail 4
4-46
4.15 Floating Point And Scientific Notation
PLC’s can use man
different s
stems and methods to store data.
The most common have alread
been discussed in previous sections e.
. BCD, Binar
,
Decimal, Hex. These are what is known as ‘inte
er’ formats or ‘whole number formats’.
As the titles su
est these formats use onl
whole numbers with no representation of fractional
parts. However, there are two further formats which are becomin
increasin
l
important and
the
are:
a) Floatin
point and
b) Scientific notation
Both of these formats are in fact closel
related. The
both lend themselves to creatin
ver
lar
e or ver
small numbers which can describe both whole and fractional components.
General note:
• Sometimes the words ‘Format’, ‘Mode’ and ‘Notation’ are interchan
ed when descrip-
tions of these numerical processes are made. However, all of these words are providin
the same descriptive value and as such users should be aware of their existence.
Some useful constants
π
3.141 10
0
2
π
6.283 10
0
π
/4 7.853 10
-1
π
2
9.869 10
0
The speed of li
ht 2.997 10
8
m/s
Gravit
,
9.807 10
0
m/s
2
e 2.718 10
0
Fixed points:
Boilin
point of liquid ox
en -1.8297 10
2
°
C
Meltin
point of ice 0.00 10
0
°
C
Triple point of water 1.00 10
-2
°
C
Boilin
point of water 1.00 10
2
°
C
