Modeling of microsystem flow sensor based on thermal time-of-flight mode

This paper reports the results of the modeling silicon microsystem flow sensor based on Thermal Time-Of-Flight (TTOF) mode. The basic heat transfer equations and the modeling approach are first presented. The problem domain is decomposed into two subdomains which represent the fluid and the sensor chip structure, respectively. The thermal boundary layer where the interaction between the two subdomains is taking place is modeled using flow-dependent equivalent thermal resistance elements. The two subdomains and the boundary layer are subsequently implemented using the combination of SPICE and analog HDL. An experimental chip of silicon thermal flow sensor is used to validate the present model. The model has been used to predict the behavior of the flow sensor in free-running TTOF mode and also in Thermal-Convection Delay-Line Oscillator (TC-DLO) mode. Both the agreement and discrepancy found between the model and the experiments are shown and discussed.