title: A multicouple probe for temperature gradient measurements in biological materials.
abstract: An easy-to-make, sensitive, thin, flexible, multisensor probe for in vivo tissue temperature profile measurement is described. It is essentially a multijunction thermocouple (i.e., a multicouple) of type-T composition. Enamel-insulated copper wires (38 gauge) were soldered 5 mm apart to one common uninsulated constantan wire (36 gauge) and introduced into a polyethylene tube sealed at one end. The total outside diameter of the multicouple probe is less than 1 mm, and the maximum number of junctions using the specified wire sizes is approximately 16. This design permits the instantaneous measurement of a tissue temperature profile at 5-mm intervals over a distance of approximately 8 cm. An extensive calibration for the thermal conductivity effect (k effect) along the multicouple wires by means of a limb model is presented. The results show that the temperature readings of the individual junctions are significantly affected by the k effect when a thermal gradient exists along the multicouple, as is usually the case during tissue temperature measurements. However, calibration of the multicouple for the k effect yields a measurement accuracy of +/- 0.1 degree C under a wide range of gradients. This probe can be implanted in tissues to measure thermal gradients under different physiological conditions.
authors.affiliation: Department of Physiology, Faculty of Medicine, University of Toronto, Ontario, Canada.
authors.forename: M B
authors.initials: MB
authors.lastname: Ducharme
authors.forename: J
authors.initials: J
authors.lastname: Frim
mesh_terms: D000818:Animals; D001831:Body Temperature; D004582:Electronics, Medical; D005121:Extremities; D006801:Humans; D008954:Models, Biological; D013814:Thermal Conductivity; D013821:Thermometers