MONOLITHIC FLOW SENSOR FOR MEASURING MILLILITER PER MINUTE LIQUID FLOW

A flowmeter based on a monolithic integrated flow sensor has been developed for measuring liquid flows as small as 0.1 ml/min in microchannels. The flowmeter is able to operate in thermal transit-time mode and thermal dilution mode. Diodes on the silicon chip are used both as the heating device and as the temperature detectors. When operating in thermal transit-time mode, the flowmeter has an accuracy better than 0.2% (at a flow rate of 0.2 ml/min) and a 90% response time less than 1 s. While operating in thermal dilution mode, the flowmeter has an accuracy of about 1%, but features an excellent dynamic performance with a -3 dB frequency cutoff up to 5 Hz. A dynamic model has also been developed for the interpretation of the mechanism of the flow sensor and for the calibration of the flowmeter. Simulation based on the model shows good agreement with the experimental results. The flowmeter will be used to monitor and control the liquid flow in FIA (flow injection analysis) systems.