THERMOCOUPLE_PREAMPLIFIER

Published:2009/7/7 9:11:00 Author:May | From:SeekIC

The MAX420 is operated at a gain of 191 to convert the 52 μV/'℃ output of the type J thermo-couple to a 10 mV/℃ signal. The -2.2 mV/℃ tempco of the 2N3904 is added into the summing junction with a gain of 42.2 to provide cold-junction compensation. The ICL8069 is used to remove the offset caused by the 600-mV initial voltage of the 2N3904. Adjust the 10-KΩ trimpot for the proper reading with the 2N3904 and isothermal connection block at a temperature near the center of the cir-cuit's operating range. Use the component values shown in parentheses when using a type K thermo-couple.



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