Thermal and electrical characterization of a micro-hotplate for calorimetry

Abstract

This thesis characterizes a micro-hotplate designed at Draper Laboratory. This hotplate will be integrated into a calorimetry system that measures the heat released or absorbed by a reaction. An analytical thermal model is developed to quantify the heat transfer mechanisms between the hotplate and the environment. The analytical model is verified through experimental measurements conducted with the device operating in both ambient conditions and vacuum. In ambient conditions, the heat transfer is dominated by air conduction as predicted by the model. Air conduction can be reduced by operating the device in a medium with a lower thermal conductivity. The relatively short timescale over which the hotplate comes to thermal equilibrium with the environment limits the types of reactions that can be measured with the device. The performance of the hotplate can be improved by operating it in vacuum, by constructing it from a material with a lower emissivity, or by decreasing its surface area. The noise spectral density of the hotplate's resistive temperature sensor is characterized. The hotplate's ability to resolve temperature is limited by the flicker noise in the sensor.