Thermal asymmetry compensation of a wind sensor fabricated on ceramic substrate

A wind sensor, with power adjustment for non-ideal packaging compensation, is reported. In order to achieve high reliability and moderate sensitivity, a lift-off process was adopted to fabricate the chip on ceramic substrate directly. Two Platinum/Titanium resistors surround together in the center of the chip. One is introduced to heat the sensor higher than the ambient temperature to a constant value, and the other is used to detect the average temperature of the sensor. The heat distribution is detected by four Platinum/Titanium resistors, located symmetrically on the chip. The thermal asymmetric distribution in the sensor, due to non-ideal packaging in different heating power and in different ambient temperature was sampled by a Micro Control Unit (MCU) at the zero wind speed. An expression of the thermal asymmetry was obtained to provide feedback signals to adjust the heating power of four auxiliary heaters, which are located on the sensor beside the heat distribution detection resistors, to cancel the affect of thermal asymmetry. After compensation by power distribution adjustment, the output signal fluctuation is reduced to 10mV, and the absolute error of wind direction testing is less than 2 degrees.