Appendix F: Profibus Pa Profile Structure; Profibus Level Device Design; Block Model - Siemens Sitrans LR250 Instruction Manual

Appendix F: PROFIBUS PA Profile
Structure

PROFIBUS Level Device Design

The device follows the profile block model and is implemented as a Profile 3.0, Class B,
PA device. Standard profile parameters are used to program the level transducer block.

Block Model

The Block Model represents how measured values are recorded and processed. All data
is viewed from the perspective of the DCS or PLC, so information from the sensor is an
input.
The functions of the device are divided into blocks with different areas of responsibility.
The blocks are configured by parameters modified via SIMATIC PDM.
The device is implemented with one Physical Block, one Transducer Block (TB), and two
Analog Input Function Blocks (AIFB1 and AIFB2).
Physical Block
The Physical Block handles functionality and descriptions relating to the device as a
whole: for example, LCD Contrast (functionality) and Firmware Revision and Tag
(descriptions).
sensor
Transducer Block (TB)
The Transducer Block carries out adjustments to the sensor, such as level calibration and
volume calibration. It supplies the outputs utilized by either or both of the AIFBs.
Analog Input Function Blocks AIFB1 and AIFB2
The two AIFBs are completely independent of each other. They utilize the output from the
Transducer Block, and apply any required quality checks, scaling, and Fail-safe operation
selections.
The output of an Analog Input Function Block supplies the measured value and
associated status information to PROFIBUS PA via cyclic data transfer.
Page 128 SITRANS LR250 (PROFIBUS PA) – INSTRUCTION MANUAL
sensor
electronics
temperature
Transducer Block
Analog Input
Function Block1
Analog Input
Function Block2
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