Keysight Technologies 3458A Guide D'utilisation page 142

4 Making Measurements
SREAL example
This example resolves the decimal equivalent of the following SREAL formatted
number:
SEEEEEEE EMMMMMMM MMMMMMMM MMMMMMMM
10111011 11001000 01001000 10010000
The sign bit "S" is set "1," this indicates that the number is negative.
The base two's exponent (01110111) evaluates to:
6
2
Since the exponent is biased by 127, the real value is:
exponent - 127 = 119 - 127 = -8
The mantissa [1.10010000100100010010000 (MSB assumed "1")] evaluates to:
1 +2
Evaluating the mantissa at the byte level instead of the bit level:
byte 1
11001000 01001000 10010000
mantissa =200
or
mantissa = (200
The SREAL number is then calculated by:
-1
Double real
The double real (DREAL) format conforms to IEEE-754 specifications and contains
64 bits (8 bytes) per reading as follows:
S EEE EEEE
MMMM MMMM
Where:
142
5 4 2 1
+ 2 + 2 + 2 + 2 + 2
-1 -4 -9 -12
+ 2 + 2 + 2
byte 2 byte 3 = byte 1
-7
×
2 + 72
16
×
2 + 72
-8
× ×
2 1.56471443177 = -6.1121657491E-3
byte 0 byte 1
EEEE MMMM
byte 4 byte 5
MMMM MMMM
0
= 119
-16 -19
+ 2 + 2 = 1.56471443177
byte 2
200 72
-15 -23
× ×
2 + 144 2
8 -23
× ×
2 + 144) 2
byte 2 byte 3
MMMM MMMM MMMM MMMM
byte 6 byte 7
MMMM MMMM MMMM MMMM
byte 3
144
= 1.56471443177
= 1.56471443177
Keysight 3458A User's Guide