A Closed-Loop Mass Flow Controller Based on Static Solid-State Devices

Abstract

A mass flow controller, based on an integrated flow sensor and a thermally actuated solid state regulator, is presented. The sensor is a miniaturized differential calorimeter obtained by postprocessing a silicon chip fabricated by a standard microelectronic process. The regulator consists in a microchannel etched into the surface of a silicon substrate and sealed with a glass plate, joined to the silicon die using anodic bonding. Flow regulation is achieved by varying the channel temperature by means of a chromium resistor. The two devices are connected in closed-loop through a low noise—low offset electronic circuit. Experimental data, demonstrating the effectiveness of the flow controller, are presented. Limitations of the proposed approach and possible improvements are discussed

Design Issues for Low Power Integrated Thermal Flow Sensors with Ultra-Wide Dynamic Range and Low Insertion Loss

“…These properties, partly due to their differential structure, are fundamental in applications involving the measure and control of very low flow rates. This is the case, for example, of gas distribution lines in semiconductor manufacturing equipments [9], fuel/air mixing system in car engines [10] and propellant feed system in thrusters on board satellites [11,12]. Recently, very sensitive integrated flow sensors have been proposed for the development of a directional wind sensor, with robustness, power consumption and miniaturization characteristics suitable for application in wireless sensor networks [13].…”

Numerical Study on Characteristics of Convection and Temperature Evolution in Microchannel of Thermal Flowmeter

“…Thermal flowmeters, specifically calorimetric flowmeters, are widely used in a variety of industrial manufacturing, aerospace, biomedical engineering, and other fields. Because of their compact size, quick response time, and low energy consumption, they are particularly useful for microflow rate measurements [ 1 , 2 ]. The thermal flowmeter works as follows: when the working medium flows over the upstream and downstream heat sources inside the thermal flowmeter channel successively, heat is carried by the flow simultaneously, resulting in a temperature difference between the upstream and downstream heat sources.…”

A single chip, double channel thermal flow meter

“…The method to convey the gas flow to the sensing structure without damaging the bonding wires and introduce as low as possible insertion losses has to be tailored to the particular application, taking into account specification of sealing, sensitivity, range and miniaturization (Bruschi et al 2007). Solutions based on placing the whole chip with its bonding wires inside the gas channel (Mayer et al 1995;Bruschi et al 2006) are not compatible with liquid flows or aggressive gases; furthermore, the channel cross-section cannot be reduced below several mm 2 , so that, handling of very small flows is limited. On the opposite side, the alternative is placing the chip outside the flow channel, relying on a thermally conducting membrane or simply the pipe walls to allow heat exchange between the sensor elements and the fluid.…”