Bilateral comparison for determining the dynamic characteristic values of contact thermometers in fluids

In applicable standards and sets of rules (VDI/VDE, 2014; DIN, 2010, 2017), recommendations are made concerning the types of experiments for determining the dynamic parameters in fluids (flowing water and flowing air) under well-defined conditions. In the data sheets of the thermometer manufacturers, quite different specifications can be found, such as time percentage values or time constants. Only a few thermometer manufacturers specify the medium and flow conditions under which these parameters have been determined. Above all, it is not common practice to indicate a measurement uncertainty for the dynamic parameters found. In Augustin et al. (2017), a first model for the indication of the measurement uncertainty of dynamic parameters in flowing air was presented. The present paper describes the results of a bilateral comparison made for the first time for determining dynamic parameters in the laboratories of the JUMO GmbH & Co. KG Fulda company and at the Institute of Process Measurement and Sensor Technology of the TU Ilmenau. In doing so, two type-N thermocouples with different diameters were investigated in experimental facilities with flowing water and flowing air. Subsequently, the dynamic parameters found were compared with each other. The differences revealed mainly resulted from plant-specific parameters.