Temperature measurement technology

TU Ilmenau

Miniaturized fixed-point cells integrated in thermometers allow for the first time direct in-situ calibration of thermometers with direct connection to the ITS-90 in process.  Research in this field over the last 20 years has made a significant step towards more practical and industrially applicable fixed point calibrations. In Germany the Institute of Process Measurement and Sensor Technology is the only research institution with comprehensive know-how in this field. Together with an industrial partner, this competence has been extended to include the continuous single-point calibration of a thermometer directly in process using a reference material integrated into the thermometer, whose Curie temperature TC = 118 °C provides the reference temperature for the calibration.

Literature:

• BERNHARD, F.; BOGUHN, D.; AUGUSTIN, S.; MAMMEN, H.; DONIN, A.: Einsatzerfahrungen mit selbstkalibrierenden Thermoelementen im Kraftwerkseinsatz. In: Temperatur 2003. Berlin: VdI-Verlag, 2003, S. 259–266
• BERNHARD, F.; AUGUSTIN, S.; MAMMEN, H.: Application of Self-Calibrating Thermometers with Miniture Fixed-Point Cells in a Temperature Range from 300 °C to 650 °C. In: TEMPMEKO 2004. Dubrovnik, 2004
• SCHALLES, M.; VRDOLJAK, P.: Kalibrierung von Thermometern in situ im Prozess. In:  Sensoren und Messsysteme / Fachtagung Sensoren und Messsysteme 19. 2018 Nürnberg. - Berlin : VDE Verlag GmbH, 2018, Seite 219-222

TU Ilmenau

At the institute, various test facilities have been set up to investigate the static and dynamic behaviour of contact thermometers in accordance with applicable standards and guidelines. They serve on the one hand to compare the characteristic values of different thermometer designs, but also to validate the results obtained with numerical methods. The dependence of the characteristic values on the temperature-dependent material properties as well as on different medium, installation and environmental conditions is determined both theoretically by numerical calculations and practically. The results of the research work were incorporated into various standards and guidelines (e.g. VDI/VDE GMA Guideline 3522 "Dynamic behaviour of contact thermometers"). The test facilities are available for measurements in the service sector.

Literature:

• AUGUSTIN, S.; FROEHLICH, T.: Temperature dependence of dynamic parameters of contact thermometers. In: Sensors. MDPI, Bd. 19 (2019), DOI: 10.3390/s19102299
• AUGUSTIN, S.; FROEHLICH, T.; SCHALLES, M.; KRUMMECK, S.: Bilateral comparison for determining the dynamic characteristic values of contact thermometers in fluids. In: Journal of sensors and sensor systems. Bd. 7, 2018, Seite 331-337
• AUGUSTIN, S.; FROEHLICH, T.: Dynamisches Verhalten von Berührungsthermometern unter Berücksichtigung der Temperaturabhängigkeit der Materialdaten – Erweiterung der VDI/VDE-Richtlinie 3522. In: Technisches Messen. Bd. 83, 2016, 7-8, Seite 402-409
• AUGUSTIN, S.; BERNHARD, F.: Numerical calculation of static and dynamic parameters of industrial temperature sensors. In: Measurement / International Measurement Confederation. Elsevier Science, Bd. 17, 1996, 4, Seite 217-228

TU Ilmenau

When contact surface temperature measurement is carried out with touch probe or pipe contact thermometers, other factors influencing the static and dynamic characteristics of the thermometers than when measuring in fluids must be taken into account (e.g. contact pressure, surface roughness, etc.). For this reason, special calibration devices have been developed for the calibration or determination of thermal measurement deviations and set up in cooperation with various partners from industry and PTB.

The same applies to the development of different calibration stations for radiation thermometers as well as heat flow sensors. In some cases, the triple fixed-point cells developed at the institute were used, which allow an immediate traceability of the calibration to the International Temperature Scale ITS-90.  

At the institute, the different influencing factors in the measurement with surface thermometers as well as heat flux sensors were identified and their contributions to the corresponding measurement uncertainty budgets were determined comprehensively by experiments. This work formed an important basis for the development of new guideline documents in this field.

Literature:

• BERNHARD. F.; AUGUSTIN, S.; MAMMEN, H.; SOMMER, K.-D.; TEGELER, E.; WAGNER, M.; DEMISCH, U.; TRAGESER, P.: Calibration of contacting sensors for temperature measurements on surfaces. In: Proceedings of TEMPMEKO '99, the 7th International Symposium on Temperature and Thermal Measurement in Industry and Science; June 1999, Delft, Seite 257-262
• SCHALLES, M.: Dreifach-Fixpunktstrahler zur Kalibrierung von Strahlungsthermometern, Technische Universität Ilmenau, Dissertation, 2009
• SCHALLES, M.; BERNHARD, F.: Triple-fixed-point blackbody for the calibration of radiation thermometers. In: Int. Journal of Thermophysics 28 (2007), Nr. 6, S. 2049–2058
• HOHMANN, M.; MARIN, S.; SCHALLES, M.; FROEHLICH, T.: Dry block calibrator with improved temperature field and integrated fixed-point cells. In: International journal of thermophysics. Bd. 38 (2017), 2, Article 17, insges. 10 S., DOI: 10.1007/s10765-016-2155-9
• HOHMANN, M.; MARIN, S.; SCHALLES, M.; FROEHLICH, T.: Dry block calibrator with improved temperature field and integrated fixed-point cells. In: International journal of thermophysics. Bd. 38 (2017), 2, Article 17, insges. 10 S., DOI: 10.1007/s10765-016-2155-9
• HOHMANN, M.: Realisierung eines Blockkalibrators mit Wärmestromsensoren und integrierten Fixpunktzellen, Technische Universität Ilmenau, Dissertation, 2016
• PUFKE, M.: Messtechnische Untersuchung von Rohranlegethermometern. Technische Universität Ilmenau, Dissertation, 2019
• PUFKE, M.; FROEHLICH, T.: Einflussfaktoren auf die Messung mit Rohranlegethermometern. In: Technisches Messen. Bd. 86, 2019, 1, Seite 67-71
• KUEHNEL, P.: Kalibrierstrahler für Wärmebildkameras. Technische Universität Ilmenau, Masterarbeit, 2019

TU Ilmenau

Thermal modeling is important in almost all research work in the field of thermometry, but also in the development of precision measuring instruments where temperature is a disturbance of the measurement. Analytical as well as FEM solution methods are used for static and dynamic thermal but also coupled calculations.

The simulated systems are optimized with respect to static and dynamic thermal properties. For this purpose, parameters are formed from the geometry and the material properties, which are varied by means of stochastic calculations. Simulated results are validated on the basis of measurements using the different test equipment. The use of stochastic methods, including the Monte Carlo method, is later applied to calculate measurement uncertainties.

Literature:

• MARIN, S.; FROEHLICH, T.: Ansatz zur Bestimmung der Unsicherheit und Prognosefähigkeit eines FEM-Simulationsmodells einer kleinen Mehrfachfixpunktzelle für Kalibrierung von Berührungsthermometern. In: Technisches Messen. Bd. 85, 2018, 1, Seite 86-94
• WEIS, H. S.; AUGUSTIN, S.: Simulation of thermal behavior in high-precision measurement instruments. In: International Journal of Thermophysics 29 (2008), Nr. 3, S. 1184–1192
• FRÖHLICH, T.: Temperaturkompensation von Präzisionsmeßgeräten, Technische Universität Ilmenau, Habilitation, 2006
• AUGUSTIN, S.; BERNHARD, F.: Numerical calculation of static and dynamic parameters of industrial temperature sensors. In: Measurement / International Measurement Confederation. Elsevier Science, Bd. 17, 1996, 4, Seite 217-228

The qualitative comparison of measuring instruments and measurements is only possible if measurement uncertainties are stated, which were determined by means of measurement uncertainty considerations. The well-founded determination of measurement uncertainty is therefore a component of all research work at the institute.

Literature:

• FRÖHLICH, G.; HILBRUNNER, F.; GÜNTHER, F.: Kennlinienstabilität von Pt100-Flachmeßwiderständen im praktischen Einsatz. In: Temperatur 2003. Berlin, 2003
• SCHALLES, M.: Uncertainty budget for the temperature realisation with a triple-fixedpoint-blackbody. In: Accreditation and Qualtity Assurance 14 (2009), Nr. 6, S. 313–317. – Uncertainty Conference 2008 NOV 12-13, 2008 Erfurt, GERMANY
• KRAPF, G.: Messunsicherheiten bei Präzisionsmessungen mit industriellen Widerstandsthermometern. In: Messunsicherheit praxisgerecht bestimmen. Erfurt, 2008
• AUGUSTIN, S.; FROEHLICH, F.; HEYDRICH, M.: Bestimmung der Messunsicherheit dynamischer Kennwerte von Berührungsthermometern in strömender Luft. In: Technisches Messen. Bd. 84, 2017, 2, Seite 73-82
• SCHALLES, M.; HOHMANN, M.: Ermittlung der Unsicherheit von Thermometerkennlinien mittels Monte-Carlo-Simulation. In: Temperatur 2017 / Fachtagung Temperatur 2017 Berlin. PTB, Physikalisch-Technische Bundesanstalt, 03/17, Seite 309-314