Errors in Skin Temperature Measurements

Numerical simulation is used to investigate the accuracy of a widely used direct-contact device for measuring skin-surface temperature. The device incorporates a foam pad which functions as a de facto thermal resistance to heat flow from the skin surface to the environment. The temperature at the interface of the measurement device and the skin surface is sensed by a micro thermocouple or thermistor. The multidimensional bioheat equation was solved numerically to obtain the temperature field both in the tissue beneath the device and in the device proper. Parametric variations were made of the thermal conductivity of the foam pad and of the blood perfusion rate. Of these, the former was found to have the greater effect on the results. In the limiting case where the thermal conductivity of the foam pad is zero, an error of 1.5 °C in the measured temperature was identified. For foam pad conductivities of 0.03 and 0.06 W/m-°C, the numerical solutions gave temperature measurement errors of 0.5 and 0.15 °C, respectively.