Abstract
A novel method uses no orifices or moving parts but rather dual glass-encapsulated thermistor probes to impart a heat pulse into the flowing liquid and to detect its arrival down-stream. Detection triggers a subsequent upstream thermal pulse and the cycle repeats. The time of flight of the warmed zone is thus inversely related to liquid flow and the digital output is inherently computer compatible. A key to achieving dependable operation is electronic double time differentiation of sensor output to reject characteristically slower ambient thermal drift and to minimize response time in preparation for subsequent pulse detection. The meter is capable of measuring liquid flow rates between 0.1 and 10.0 cm/sup 3//min with a precision of at least 0.1% (sigma). The flow cell's glass and inert plastic composition makes it highly corrosion resistant. Besides its general utility in flow metering, this method is especially well suited to high performance liquid chromatography applications. 6 figures, 1 table.
Published Version
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