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Entry type: Application example Entry ID: 23642357, Entry date: 09/04/2006

S7-300/400 CPUs: Pressure Measurement in the S7-CPU Using SITRANS P Transmitter

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Almost everywhere where products or materials are processed or worked, the pressure has a decisive influence on the quality of the final product and the course of the process respectively. Concerning safety regulations, pressure monitoring is frequently essential in industrial processes. Levels of liquids can be conveniently determined via a hydrostatic pressure measurement. It is thus necessary to detect pressures, to interpret their influence and to specifically react to changes in pressure using control technology.


The device combination of SIMATIC products and SIEMENS pressure transmitters is an excellent solution to the mentioned problem. In this application, the pressure of a liquid or gas is detected with a SITRANS P pressure transmitter and converted into an injected current (4...20 mA) which is supplied to the analog input of a compact CPU. The current pressure measurement value is displayed both numerically and as a bar chart on a TP170A touch panel.



Using the special STEP7 application software, which you can download (see below), it is additionally possible to ...

  • define seven pressure ranges in the measuring range of the pressure sensor. In which of these ranges the current pressure is located is displayed on the touch panel and represented by DO bits. These bits can be used to trigger various user actions.

  • display pressure limit violations (below/above minimum/maximum pressure) which require acknowledgement, react to them (in the program) and acknowledge them.

  • provide the last pressure limit violation (below or above) with a time stamp.


The WinCC flexible configuration of the TP170A is integrated in the STEP7 project. The user interface languages German and English can be selected.



Content of Downloads


Documentation (German) 
Application Description
23642357_Druckmessung_DOKU_V20_d.pdf ( 1591 KB )
Documentation (English)
Application Description
23642357_Druckmessung_DOKU_V20_e.pdf ( 1719 KB )
STEP7 Project
23642357_Druckmessung_CODE_V20.zip ( 3209 KB )




12/2002 First edition (V1.0)
07/2006 Second edition (V2.0) complete revision and update


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