Thermocouple_cold_junction_compensation_single_supply

Published:2009/7/24 3:05:00 Author:Jessie | From:SeekIC

Pig. 13-38 In this single-supply circuit, R3 and R4 divide down the 10-mV/°K output of the LM335 to match the Seebeck coefficient of the thermocouple. The LM329B and associated voltage divider provide a voltage to buck out the 0℃ output of the LM335. To calibrate, adjust R1 so that V1 (across R4) equals the thermocouple Seebeck coefficient (in μV/℃) times the ambient temperature in degrees Kelvin (note that absolute zero in the Kelvin scale -273.18℃). Then, adjust R, so thatV1- V2 (across R6) is equal to the thermocouple output voltage at the known ambient temperature. Note that the term ∞ is used to determine R4 and R6 is the Seebeck coefficient for the type of thermocouple selected (types J, T, K, or S). National Semtconductor Linear Applications Handbook 1991 p 523.



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