Single-element thermal flow sensor using dual-slope control scheme

Abstract

Flow rate sensors for in situ gas or liquid monitoring typically comprise multiple transducer elements, including a heater and one or more temperature sensors to measure the rate of heat energy removal by the flowing fluid. The need for multiple transducer elements limits feasibility of shrinking these sensors to microfluidic flow channels and drives fabrication complexity. In this work, a thermal flow sensor architecture is presented that uses a single, resistive transducer element to measure fluid flow with a two-phase control and measurement algorithm. Experimental results demonstrate feasibility of the flow sensor architecture using a micron-scale resistor structure for measuring air flow. By separating heating and temperature measurement in time, instead of in space, this method significantly decreases required transducer area and can be further scaled for use in micro- and nanofluidic channels.