1 + mantissa) value = (-1) – KROHNE H250 M9 PROFIBUS PA EN User Manual
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Supplement to Installation and Operating Instructions H 250/ESK3-PA
2.2
PROFIBUS-PA profile
The ESK3-PA signal converter supports PROFIBUS-PA Profile Version 3.0. Moreover,
additional relevant parameters available in the device are offered via the PROFIBUS-PA
interface. The blocks made available are:
••
1 function block analog input (AI(0)):
Volume flowrate (standard)
can be changed over via “channel_parameter” to mass flowrate.
••
2 function blocks totalizer (TOT(0) and TOT(1)):
TOT(0) totalized volume (standard)
TOT(1) totalized mass (only in manufacturer-specific configuration)
••
1 transducer block for variable-area flowmeters. This block makes the parameters and
functions available which are defined in Profile 3.0,
+ additional device-specific parameters.
••
1 physical block
This block contains the parameters defined in Profile 3.0
+ additional device-specific parameters
2.3
Meaning of measured-value and status information
When integrating the device into the PROFIBUS master using GSD, you can enter which
measured values and count values should be cyclically transmitted via the PROFIBUS. Each
value is given a status. First the 4 bytes for the value are transmitted (float format in
conformance with IEEE standard 754 short real number) and then 1 byte for the status.
That means, each measurement or count value is displayed by 5 bytes. The values are
transmitted one after another in the sequence set up with the help of GSD. If, for example,
1 AI-FB and 2 TOT-FB were specified, then 15 bytes of useful data are transmitted.
First an example regarding the applied float format:
Byte n
Byte n+1
Byte n+2
Byte n+3
Bit 7 Bit 6
Bit 0
Bit
7
Bit 6
Bit 0 Bit 7
Bit 0 Bit 7
Bit 0
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
2
-1
2
-2
2
-3
2
-4
2
-5
2
-6
2
-7
2
-8
2
-9
2
-10
2
-11
2
-12
2
-13
2
-14
2
-15
2
-16
2
-17
2
-18
2
-19
2
-20
2
-21
2
-22
2
-23
VZ
Exponent
Mantissa
Mantissa
Mantissa
Example:
40 F0 00 00 (hex) = 0100 0000 1111 0000 0000 0000 0000 0000 (binary)
Formula:
Value
= (-1)
VZ
* 2
(Exponent - 127)
* (1 + Mantissa)
Value
= (-1)
0
* 2
(129 - 127)
* (1 + 2
-1
+ 2
-2
+ 2
-3
)
Value
= 1 * 4 * (1 + 0.5 + 0.25 + 0.125)
Value
= 7.5