With the combination of micropumps and flow sensors, highly accurate and secure\nclosed-loop controlled micro dosing systems for liquids are possible. Implementing a single stroke\nbased control mode with piezoelectrically driven micro diaphragm pumps can provide a solution for\ndosing of volumes down to nanoliters or variable average flow rates in the range of nL/min to Ã?¼L/min.\nHowever, sensor technologies feature a yet undetermined accuracy for measuring highly pulsatile\nmicropump flow. Two miniaturizable in-line sensor types providing electrical readoutââ?¬â?differential\npressure based flow sensors and thermal calorimetric flow sensorsââ?¬â?are evaluated for their suitability\nof combining them with mircopumps. Single stroke based calibration of the sensors was carried\nout with a new method, comparing displacement volumes and sensor flow volumes. Limitations of\naccuracy and performance for single stroke based flow control are described. Results showed that\nbesides particle robustness of sensors, controlling resistive and capacitive damping are key aspects for\nsetting up reproducible and reliable liquid dosing systems. Depending on the required average flow\nor defined volume, dosing systems with an accuracy of better than 5% for the differential pressure\nbased sensor and better than 6.5% for the thermal calorimeter were achieved.
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