Thermodynamic sensors new opportunities for measuring and control in industrial applications

This paper deals with new developed thick film sensor based on powerful thermodynamic method using the high resistance ratio-metric sensor, which is improving the accuracy of the temperature measurement. This solution minimizes usual problems as dependance of sensor's sensitivity from other factors as power supply instability, ambient temperature shift, humidity and pressure changes, effect of self heating, aging, etc. The modified low resistance sensor and relatively simple evaluating circuit were developed, realized and tested for the monitoring of activities in processes. The explicit function between sensors element and stated of monitored object were defined. Temperature radiation monitoring was chosen for the explanation of thermodynamic sensor principle. Initial thermodynamic balance equilibrium is based on equivalence of sensor elements active part power dissipation and heat flow at the sensors borders. Temperature of mounted object which is changing between two steady states can be calculated. Sensor design and its technical parameters are described. High sensitivity, short time response constant and long time stability were proved. The sensor is realized as thick film hybrid system on ceramic alumina substrate and offers a cheap but precise alternative to micro-calorimetric techniques used all above for temperature regulation. Common ESL thick film pastes were applied to realize this sensor in usual thick film process in air atmosphere using BTU thick film furnace without protecting atmosphere. There were designed different topologies and temperature models (using ANSYS) to achive optimizedconfiguration of complete sensor system. For example the temperature radiation detector can be used in many of industrial applications for distance monitoring of stationer or moving heat sources. This detector can be used also for state monitoring of hot working materials in continual industrial processes for example wire drawing, sheetingout, crystal pulling, profiles extrusion, fiberglass manufacturing, etc. Some of these applications are already tested in real industrial conditions.