Convection-based tilt sensor with minimized temperature fluctuation

This paper presents a simple and novel method for minimizing the performance dependence of a convection-based tilt sensor on environmental temperature fluctuation. Previously reported convective tilt sensors show considerable fluctuation in output voltage because of various external thermal effects. Therefore, it is necessary to have a complex circuit to compensate the external temperature fluctuation or an additional cautious package to reduce the thermal effect. In this paper, a convective tilt sensor that inhibits the environmental thermal effect without an additional circuit or package is discussed. An integrated thin-film-based thermoelectric device is utilized not only for heating an encapsulated air medium with a symmetric temperature profile when it is balanced, but also for minimizing external thermal effects. The hot junction of the thermoelectric device operates as a heater and the cold one keeps the temperature difference between two junctions constant regardless of the external thermal environment. The proposed tilt sensor showed a fairly linear output voltage within the inclination range of ±90° on two axes and even exhibited a consistent output voltage under various external temperature conditions. The fluctuation rate of the proposed tilt sensor was kept within less than 2% of the output voltage; this was even the case for a temperature range of 25 to 60 °C.