LM135 thermocouple cold junction compensation temperature measurement circuit

Published:2011/3/17 1:55:00 Author:Joan | Keyword: thermocouple, cold junction compensation, temperature measurement | From:SeekIC

The figure is a practical circuit with a wide temperature measurement range using thermocouple. It uses indexing number for K thermocouple, measuring maximum temperature up to 1000 ℃. In order to eliminate the environmental impact of the Thermocouple cold junction, LM335 is used to measure the cold junction temperature, and then the operational amplifier LM308 amplifies output voltage after superposition of the temperature voltage signal and thermoelectric power generated by the thermocouple, so that the output voltage signal reflects the true temperature of the thermocouple working end. As the LM335 output voltage is proportional to absolute temperature, LM329 and resistor distributed voltage generate voltage signal to offset the output voltage at 0 ℃. The corresponding relationship between the circuit output voltage and the measured temperature is adjusted 10mV / ℃ by the amplifier.



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