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Integration of IR temperature sensors into Siemens PLC environment
The non-contact temperature measurement devices of the feature advanced interface concepts which allow an easy integration within networks and automated systems. The following technical note highlights the setup of thermal imagers via an RS485 module as well as of online infrared thermometers via PLC using PROFIBUS DP.
Regarding PLC environments the PROFIBUS is generally accepted as one of the most used bus system. Concerning the production, process and building automation, the bus system represents an ideal, secure and fast communication exchange between the single bus partners and the control units. The set up of the PROFIBUS network is almost the same every time. On the one side you can find the control unit, e.g. a SIMATIC S7 of SIEMENS – also called master system or active station. On the other site you can find the bus partners, the so called slaves – also know as passive stations. This can either be actors or sensors. All SK infrared temperature sensors belong to the processor field communication – especially to the version PROFIBUS DP.
Integration of PI thermal imaging camera
There is now an easy solution available to integrate the thermal imager PI into PLC environments. The solutionis based on the great advantage of the master system to support the connectivity to other networks such as RS485. This enables the system setup covering long distances (up to 3 km) between the infrared camera and the PLC as you can see in the illustration above. Generally, the PI thermal imager is connected to a PC, the imager’s software PI Connect displays and analyses the temperature data. The software needs to be adjusted regarding the external communication. The RS485 connection can be chosen in the mode “Comport” via the software menu TOOLS – CONFIGURATION – EXTERNAL COMMUNICATION as it is shown in the illustration below.
The kit is available to integrate the imager into a PLC system. A virtual Comport at the PC can be created by using separate software which is included in the kit. The virtual Comport connects the software Connect with the module; the module finally transfers the data to the SIEMENS S7 PLC via A and B cables.The first illustration in this article also shows the hardware configurationbased on a connection between the SK camera and the SIEMENS S7 PLC including:
- SK160 / SK200 / SK400
- SIMATIC S7-300, CPU 313C-2 DP (processor with a PROFIBUS module)
- SIMATIC S7-300, front module with digital andanalog outputs
- SIMATIC S7-300, CP 340 (communication processor with interface)
- Software STEP 7 (to configure the SPS regarding the kit and the PROFIBUS module)
Integration of IR online thermometers
Besides the standard output signals of infrared thermometers such as voltage, power or thermocouple, SK supplies additional digital interfaces with every two pieces device (sensor head and electronic box). A free slot, available in each box, can be used to install a suitable digital interface card as you can see in the illustrations above.
The installation is very easy. A so called GSD file (a GENERICSTATION DESCRION FILE) belongs to each fieldbus partner. The file can be loaded into the PLC in order to ensure the correct communication between the master device and the slave. The GSD file for PROFIBUS interface is available on a CD supplied with the device. It contains all important information such as the communication orders to request the object temperature or to set emissivity values.
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