Design and Simulation of a Dual Axis Thermal Accelerometer using Single Axis Structure
An accelerometer detects acceleration and tilt of a device. There are several areas where accelerometers are in use, e.g. aerospace, navigation, automotive industry, electronic gadgets etc. According to different working principle, there are different types of accelerometer, e.g. piezo-electric, piezo-resistive, capacitive etc. All of these structures require solid proof mass to detect acceleration, which reduces their shock survival rating. Out of these, capacitive accelerometer is most widely used, which is difficult to integrate with CMOS platform.
There is also another type of accelerometer, known as thermal accelerometer, which does not contain solid proof mass and also can be integrated with CMOS platform. A basic thermal accelerometer contains a heater structure and two temperature sensors placed in a cavity. The temperature sensors are placed symmetrically opposite of the heater. When the heater is powered, it heats up the surrounding fluid (e.g. air). When acceleration is applied a differential temperature is detected by temperature sensors due to deformation of surrounding heated fluid.
In this paper, we are reporting a dual axis thermal accelerometer using a single axis structure. It is found from the literature that the single axis thermal accelerometer has much higher sensitivity compared to the dual axis thermal accelerometer. So, here we have designed a thermal accelerometer whose structure is close to the single axis, but acts as a dual axis accelerometer. The heater structure of the device is very simple and the device contains four temperature sensors to detect x and y axis acceleration. In this accelerometer, when we apply acceleration along x-axis its sensitivity is 1.07 K/g and along y-axis 0.23 K/g when the heater temperature is 610K. However, this difference in sensitivity between two axes can be improved through on-chip amplifiers. Thus, we believe that this work may lead to a simpler high sensitive dual axis thermal accelerometer.