Siemens SIPROTEC Manual page 44

Data of the PROFIBUS DP messages
Example
44
Only few measured values (e.g. measured values obtained via transducer input) can
be transmitted as secondary values. The conversion factor is determined automati-
cally.
In order to transmit also fractional digits in the 16-bit integer value via PROFIBUS DP,
a Scaling factor (a multiple of 10) is used. During the conversion from the internal
IEEE-Float format used in the SIPROTEC devices to the 16-bit integer value a multi-
plication with the Scaling factor takes place.
The PROFIBUS DP master must consider the chosen Scaling factor when eval-
uating the received measured value.
The following is set in the Measured value description for "3P1_V1":
• Dimension: kV
• Conversion factor (100 % correspond to): 63.5085
• No. of decimal places: 2
The number of decimal places is used for displaying the value on the device display
and is of no consequence for the transmission via PROFIBUS DP.
A selection of the Scaling factor (see below) determines the number of decimal
places significant for transfer via PROFIBUS DP.
Measured value dimensions are not transmitted via PROFIBUS DP.
The selected dimension (in this case: kV) must be indicated to the PROFIBUS DP
master for each measured value.
When allocating the measured value as "Destination system interface", the following
was selected:
• Scaling index: 1
which implies:
• Type: Primary value
• Scaling factor: 10
• Zero offset: 0
For transmission of "3P1_V1" via PROFIBUS DP this means:
• The measured value is transmitted as a primary value. The above mentioned con-
version factor of "100 % correspond to 63.50585" is used in the conversion.
• In the 16-bit integer value that is transmitted via PROFIBUS DP, one decimal place
is implied as a result of the Scaling factor equal 10 used in this example.
If for example 87.3 % of the nominal voltage (100 % value) is present, then the PROFI-
BUS DP master receives the following value:
(0.873 * 63.50585 * 10)
which based on the above mentioned settings is to be interpreted as:
55.4 kV
= (554.41)
integer integer
SIPROTEC PROFIBUS DP - Bus mapping 6MD662/3/4
= 554
C53000-L1840-B011-03