IQ 100 Series (130/140/150) Meter
App B: Modbus Map
76 User and Installation Manual IM02601003E-July 2010 www.eaton.com
Floating Point Values
Floating Point Values are represented in the following format:
Regis-
ter
0
1
Byte
0
1
0
1
Bit
7 6
5
4 3 2
1 0 7
6
5
4
3
2
1
0
7
6
5
4 3
2
1
0 7 6
5 4 3
2
1
0
Mean-
ing
s e
e
e e e
e e e
m
m
m
m
m
m
m
m
m
m
m m m
m
m m m
m m m
m
m
m
sign
exponent
mantissa
The formula to interpret a Floating Point Value is: -1
sign
x 2
exponent-127
x1.mantissa = 0x0C4E11DB9
-1
sign
x 2
137-127
x 1• 1000010001110110111001
-1 x 2
10
x 1.75871956
-1800.929
Regis-
ter
0x0C4E1
0x01DB9
Byte
0x0C4
0x0E1
0x01D
0x0B9
Bit
7 6
5
4 3 2
1 0 7
6
5
4
3
2
1
0
7
6
5
4 3
2
1
0 7 6
5 4 3
2
1
0
Mean-
ing
s e
e
e e e
e e e
m
m
m
m
m
m
m
m
m
m
m m m
m
m m m
m m m
m
m
m
sign
exponent
mantissa
1
0x089 + 137
0b011000010001110110111001
Formula Explanation:
C4E11DB9 (hex)
11000100 11100001 00011101 10111001 (binary)
The sign of the mantissa (and therefore the number) is 1, which represents a negative
value.
The Exponent is 10001001 (binary) or 137 decimal.
The Exponent is a value in excess 127. So, the Exponent value is 10.
The Mantissa is 11000010001110110111001 binary.
With the implied leading 1, the Mantissa is (1).C23B72 (hex).
The Floating Point Representation is therefore -1.75871956 times 2 to the 10.
Decimal equivalent: -1800.929
NOTES:
• Exponent = the whole number before the decimal point.
• Mantissa = the positive fraction after the decimal point.