Oscillator-Type Thermal Micro Flow Sensor

In recent years, miniaturization and higher performance have been increasingly required for the electronic devices in the measurement system or electronics. In order to accomplish these goals, sensors and actuators using the MEMS have been widely studied. A flow sensor is one of such MEMS sensors. There are various types of flow sensors such as an electromagnetic type, a float type, an ultrasonic type, an impeller type, or a thermal type. Among them the thermal type has the potential of fulfilling the above requirements and is easy to be produced using the MEMS technology. Based on these backgrounds the micro thermal flow sensor using SOI-MEMS technology has been extensively studied. The authors conducted a research on thermal micro flow sensor using SOI-MEMS technology which can easily be integrated with other sensors such as acceleration sensors. However, there are fluctuations in sensitivity and offset due to thermal stress and aged deterioration in a bridge circuit system including ordinary temperature sensitive resistors. In this paper, we investigated an oscillator type thermal micro flow sensor aimed at suppressing these effects by utilizing the time delay of thermal conduction.