FLOW_METER

Published:2009/7/9 21:00:00 Author:May | From:SeekIC

Simple opamp circuit with one transistor gives reliable hot-wire anemometer for measuring flow of gases or liquids. R2 is heated above ambient temperature in Wheatstone bridge including overheat resistor R1which is calibrated to be 30% larger than cold resistance of R2. Bridge is fed from power tran.sistor which is within feedback loop of opamp that senses bridge unbalance. Output of bridge is fed back to power transistor in correct phase for maintaining constant- temperature condition in which R2 is approximately equal to R1. Article covers construction of hot-wire probe made from Wollaston wire.-W. Bank, Build Your Own Constant-Temperature Hot-Wire Anemometer, EDN Magazine, Aug. 1, 1972, p 43.



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