PROFIBUS-DP - Parameterization in DIGSI
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SIPROTEC PROFIBUS-DP - Communication profile
C53000-L1840-B001-03
4.3 Scaling of measured values
Measured values are transferred via PROFIBUS-DP between the SIPROTEC device
and the PROFIBUS-DP master as integer values (two bytes, ref. to chap. 3.4) but they
are in general available in the SIPROTEC device in floating-point format as a percent-
age referred to the parameterized nominal values of the primary equipment.
4.3.1 Measurement conversion
Before transmission of a measured value via PROFIBUS-DP a measurement conver-
sion (scaling) must be carried out in the SIPROTEC device.
Scaling Scaling of a measured value to the format for the transmission via PROFIBUS-DP
means the definition of:
• Type,
• Scaling factor,
• Zero offset.
Type Decision, whether the measured value is transmitted as percentage value, primary
value or secondary value via PROFIBUS-DP.
Depending on the measured value not all of these three possibilities are available, e.g.
no secondary values for power values.
Scaling factor The measured value in the SIPROTEC device (floating-point format) is multiplied by
the scaling factor before transformation to an integer value (for PROFIBUS-DP).
It is possible to transfer fractional digits by multiplication by a multiple of 10 in the
integer value with that.
Zero offset The Zero offset is added to the result of the multiplication of the measured value in the
SIPROTEC device (floating-point format) by the scaling factor.
Formula The measured value in integer format for transmission via PROFIBUS-DP is calcu-
lated summarizing according to the following formula:
Measured value
Integer
= Measured value
Float
* Scaling factor + Zero offset
in which "Measured value
Float
" is a percentage value or, if necessary, changed into
primary value or secondary value before (according to the definition of Type).
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