1991 Volume 111 Issue 12 Pages 637-644
A monolithic pressure-flow sensor combining a silicon piezoresistive pressure sensor and a thermal type silicon flow sensor was fabricated and its characteristics in air were investigated. At 0_??_1 kg/cm2 and 0_??_75°C, the pressure measurement characteristics such as sensitivity, thermal sensitivity shift, nonlinearity and thermal zero shift were the same as those of a conventional piezoresistive pressure sensor. Reproducible flow output without hysteresis was obtained at 0_??_150 g/s. It was clarified from the flow visualization experiment that a bending observed in the flow calibration curve at the flow rate of 15_??_80 g/s was due to a separation bubble formed at the front of the chip. The flow output showed large measurement error during the transient change of air temperature and it also decreased with the increasing of sensor support temperature. These characteristics were well explained by thermal balance at the heater of the flow sensing part.