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A flow‐measuring system for use in small lakes 1
Author(s) -
MacIntyre Sally
Publication year - 1986
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1986.31.4.0900
Subject(s) - wheatstone bridge , thermistor , flow measurement , signal (programming language) , turbulence , mechanics , ultrasonic flow meter , bridge circuit , acoustics , flow (mathematics) , calibration , physics , laser doppler velocimetry , materials science , optics , voltage , resistor , blood flow , medicine , quantum mechanics , computer science , programming language
Currents, internal waves, and turbulence can be studied with a flowmeter consisting of a heated thermistor in a Wheatstone bridge circuit. Flow is proportional to the imbalance of the Wheatstone bridge caused by cooling of the heated thermistor bead as water flows past. Because the flow‐sensing element is spherical, speed can be measured but not direction of flow. The flowmeter can measure speeds as low as 0.1 cm s −1 and can resolve frequencies up to 5 Hz. Frequency responses were determined by comparison with a laser‐Doppler velocimeter and by spectral analysis of field data. At low speeds (<0.3 cm s −1 ), thermally driven convection contributes to the signal, but flow speeds can be estimated reliably by using a calibration equation that has as one of its parameters the voltage output at zero velocity.