THERMAL IMPEDANCE OF THICK-FILM RESISTANCE THERMOMETERS BELOW 0.2 K

Contributions to the thermal impedance of thick-film resistors (TFRs) are discussed. Measurements of the heat flow along the resistance laye r, through the substrate and through the glass overcoating, are presen ted for commercial resistors mounted on a copper plate in the 30-170 m K temperature range. Because of the relatively good thermal conductivi ty of the film material (three orders of magnitude higher than that of alumina), the contribution to the heat flow of the resistance layer i s never negligible in spite of the thinness of the latter. Suggestions are given for the best mounting of the TFRs as low-temperature thermo meters. Less conventional uses of TFRs as thermometers in bolometers a re also considered. (C) 1998 Elsevier Science Ltd.