An optimized micromachined convective accelerometer with no proof mass

Miniaturization, low cost and high performance of accelerometers have been the topic of extensive research. A kind of convective micromachined acceler ometer without proof mass is described in this paper. It consists of a micr oheater and two temperature sensors which measure the temperature differenc e between two sides of the microheater caused by the effect of acceleration on free convection. The optimization consideration is conducted before fab rication; some key factors, heater size and power, cavity size, distance be tween the heater and the sensor and the working medium, are considered. The test for the optimized device shows that the linearity error is smaller th an 0.35% under tilt conditions of natural gravity and smaller than 2% under acceleration to 10 g (g = 9.81 m. s(-2)). A sensitivity of 600 muV g(-1) i s measured for operating power of 87 mW, the response frequency is about 75 Hz and the corresponding noise equivalent acceleration is approximately 1 mg Hz(-1/2) at 25 Hz. The dependence of the sensitivity on the heating powe r is a nearly linear function and the resolution increases with heating pow er increasing.