Inclinometers are used in the automotive and construction industries, for navigation and monitoring, as well as smart mobile and intelligent wireless technology. Several solutions are available on the market that use micro-mechanical spring-mass systems or fluids. Our thermal sensor uses free convection currents to precisely measure the angle of inclination.
The thermal inclinometer uses the fact that under static heat, a free convection flow occurs that is directed upward, in the same manner that a flame from a candle wick points upward. In order to measure the temperature differentials associated with the flow, two thermometers in the form of temperature-dependent electrical resistance elements are attached symmetrically around the heater. If the heater is brought to a higher temperature level relative to the ambient temperature, then this convection flow is built up in the interior of the housing; the direction of this flow depends on the surrounding gravitational and acceleration field. If the sensor is in a horizontal position, both thermometers show the same temperature. If the sensor is tilted, then the thermometers rest on different isotherms, because the convection flow remains aligned to the gravitational field of the earth. Any movement of the sensor structure (inclination or acceleration) causes a displacement in the temperature field and flow field and thus a corresponding electrical signal.
The sensor has a very simple design, using SOI technology it can be manufactured with a few process steps, and it measures the angle of inclination in two axes. The sensor is set up on a PCB and hermetically sealed with a cover to protect it from disturbing environmental influences.