MICROPOWER_THERMOMETER

Published:2009/7/10 22:20:00 Author:May | From:SeekIC

Low power consumption makes circuit attractive for battery-operated equipment. Uses National LX5600 temperature transducer covering -55℃ to +125℃, whose output is directly propor-tionalto absolutetemperature at l0 mV/K, Both zero and scale factor ale independently selectable. Thermometer is pulsed at low duty cycle to reduce power consumption, with sample and hold usedto obtain continuous output between pulses. Supply range is 8-12 V; 8.4-V mercury battery will give over 1 year of operational Iife. Output can be used to drive meter for direct readout. MVBR Q1-Q2 drives LX5600 through R9. C1 and R3 control OFF time, and C1, R1, R4, and R7 control ON time. Q3 issample transistor. Output is 0-50 μA for 50-100°F temperature change. Formulas in box give values for other ranges.-R. C. Dobkin, Micropower Thermometer, National Semiconductor, Santa Clara, CA, 1974, LB-27.



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