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Research Centre, University of Applied Sciences Kempten , Kaufbeuren , Germany
Research Centre, University of Applied Sciences Kempten , Kaufbeuren , Germany
Production Engineering and Production Economics, University of Applied Sciences Ulm , Prittwitzstraße , Germany
Faculty of Engineering, Technical University Cluj, Northern University Centre of Baia Mare , Baia Mare , Romania
A new, freely programmable, scalable control system for academic research purposes was developed. The intention was, to have a control unit capable of handling multiple PT1000 temperature sensors at reasonable accuracy and temperature range, as well as digital input signals and providing more powerful output signals at 230V AC than conventional control units. To take full advantage of the system, control- loops are run in real time. The whole system runs independently of a personal computer. The two on- board RS232 connectors allow to connect further units to use more sensors or actuators or to connect other laboratory equipment, as required. To allow usage for long-time experiments, systematically electronic components with low failure-in-time (FIT) rate have been chosen in order to achieve high life expectancy. This paper describes the third prototype, which now provides stable measurements, and an improvement in accuracy compared to the previous designs. A rough estimation about the expected mean time between failures is given. As test case, a thermal solar system to produce hot tap water and assist heating in a single-family house was implemented. The solar fluid pump was power-controlled and several temperatures at different points in the hydraulic system were measured and used in the control algorithms. The hardware design proved suitable to test several different control strategies and their corresponding algorithms for the thermal solar system.
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