CORRECTION METHOD AND CORRECTION CIRCUIT FOR COLD JUNCTION COMPENSATION IN THERMOCOUPLE INPUT OF PROGRAMMABLE CONTROLLER

摘要

PROBLEM TO BE SOLVED: To provide a correction method and a correction circuit for cold junction compensation in a thermocouple input of a programmable controller for accurately measuring temperature of a measured position by means of the thermocouple input. SOLUTION: A CPU part 6 multiplies the number of turned-on input points by a prescribed constant "a" and adds a prescribed constant b thereto, then finds a correction value Td with a time constant t given thereto, adds this to a corresponding value Tc' obtained by converting temperature Tc near a terminal board detected by a temperature sensor 3, and correction processing is performed for accurately finding temperature Ta at a measured position X from an addition value Ta' even if it is affected by a change (input on/off, the number of turned-on input points) in the state of multipurpose input. COPYRIGHT: (C)2004,JPO