On the Importance of Temperature Coefficient of Resistance Values for Transient Measurements: Effective thermal conductivity Determined by a Hot Disk Sytsem
Presented in 1991 by Silias E. Gusstafsson, the transient plane source (TPS) technique is nowadays a commercially available product efficient in the determination of thermal conductivity and thermal diffusivity of a multitude of materials. Here, an isolated, bipolar spiral made from nickel acts as heating source and resistance thermometer. A constant heating power is applied and the resulting resistance change of the spiral-like sensor is recorded while measuring. Imagine now that the temperature rise of the material next to the sensor, which acts as a direct input in the numerical procedure, is calculated by the temperature coefficient of resistance (TCR). Thus, it gets obvious that inaccuracies in TCR values contribute significantly towards the overall uncertainty of TPS measurements. Moreover, without a calibration inhouse measurements of the insulating material SILCAL 1100 up to 700 ?C showed significant deviations referred to an intercomparision test of several laboratories especially at high temperatures. This work demonstrates the vital importance of calibrating TPS based systems by measuring the TCR values of the sensor material. In order to do so, a number of experiments have been conducted to rule out a variety of influencing parameters such as temperature field, measurement technique and sensor-specimen combination. To sum up, by accurately determining the TCR values of the system it was possible to considerably lower the gap between the inhouse measurements and the intercomparision test of the aforementioned SILCAL 1100 material. Hence, calibrating the TCR values seems mandatory for achieving trustworthy data in particular at higher temperatures.
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Pitt Goetze (POC,Primary Presenter,Author), firstname.lastname@example.org;
Simon Hummel (Co-Author), email@example.com;