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Abstract

Temperature stabilization by inertial feedback control has proven a powerful tool to create the ultra-stable environment essential for high resolution calorimetry. A thermally insulated mass, connected to a base through Seebeck effect sensors (thermopiles) is used as a reference to control the base temperature. The thermophile signal is proportional to both the heat capacity of the reference mass and the derivative of the base temperature. Using vacuum insulation the bismuth telluride thermopiles, temperature derivative sensors (TDS) were designed and tested with sensitivities up to 3300 VsK{-1}. Standard industrial controllers with approximately +/- 1mV input noise and stability, permit control of temperature derivatives to +/- 3E-10 Ks{-1}. Single cup thermoelectric calorimeters coupled to the TDS-controlled base permitted measurement of heat flow from samples in a power range from 3 mW to 10 W with high accuracy (+/-100 ppm), resolution (+/-0.2 mW) and reproducibility (+/- mW). In this paper the design of two instruments is described in detail. Their performance is demonstrated on a variety of measurements.

Additional information

Authors: HEMMERICH J L, JET Joint Undertaking, Abingdon, Oxon. (GB);MILLER A, JET Joint Undertaking, Abingdon, Oxon. (GB);LOOS J-C, Brunel University, Uxbridge (GB);MILVERTON P, UKAEA Winfrith (GB)
Bibliographic Reference: Article: JET-P(96)21 EN (1996) 17pp.
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon, OX14 3EA (GB)
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