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Pick up a piece of copper wire of thermocouple compensating lead wires with and without affect _ instrument

by:JVTIA     2020-10-30
1, thermocouple compensation wire can be tin welding! 2, if the compensation conductor should be long enough, need to replace with copper wire, must follow the 'law of middle conductor! Based on the thermocouple thermometer table thermocouple cold junction compensation method is a kind of commonly used temperature sensor, using thermoelectric effect, and according to the hot and cold end temperature difference of thermoelectric emf measuring temperature, and has high measurement precision, simple structure, convenient use. The thermometer has been widely used in the table. Common cold junction compensation method due to its complex structure, large noise, linearity error can cause great influence on measuring results. New method of thermocouple cold junction compensation principle of the method, the cold end temperature is measured by the PT1000, after A/D conversion by MCU to PC resistance through software conversion into voltage value added to the thermocouple voltage through the compensation on the block to eliminate the impact of the cold end temperature changes, thus to compensate. Compensation block design the method of cold junction compensation of the main device is a piece of good performance of thermal conductivity of aluminum. General thermocouple cold junction compensation method bridge principle of compensatory method of R1, R2, R3 resistance equal, made of manganese bronze with zero temperature coefficient approximation, namely the resistance varies with temperature, and Rt with thermocouple PT1000, with the thermocouple cold end at the same temperature, the resistance changes with the temperature, temperature, resistance to increase when the temperature of the cold end is zero R1 = R3 = = R1, R2 can make the output of the bridge is zero, if the cold end temperature, makes the thermocouple thermoelectric potential bring with the decrease of the error of measurement, but now the PT1000 resistance will also increases with temperature rise, the compensation bridge out of balance, the output value is not zero, the change in bridge output equals the thermocouple thermoelectric potential variation, and the change in the opposite direction, the two cancel each other out make the size of the total output of changes over the cold end temperature. Used in millivolt voltage generator simulation experiment data record type K thermocouple thermoelectric potential, on the circuit board to complete A/D conversion, through the MCU, upload the upper machine by the upper machine to A/D conversion value for temperature and display. This method of R1, R2, R3 accuracy requirement is high, and the noise of V +, temperature drift, higher stability, to meet the experimental requirements need to make the bridge current to a suitable value, high difficulty of debugging. When the multichannel measurement, need to decorate a multiplex device, structure is more complicated. In a cuboid aluminum piece on the horizontal axis of equidistant in turn hit three hole, and cut along the horizontal axis. To aid in the connection process after about two root pressure compensation conductor should be as two hole, hole in the middle of the pressure into the thermocouple PT1000. In the process of the pumped in order to guarantee the uniformity of heat transfer, the diameter of the thermocouple and compensation conductor should be consistent and contact fully with compensation block, insulation material to be the same. Thermocouple compensating circuit design by compensation wires to the compensation of the instrument in the block before by Cu wire connection in the circuit board. Compensation and thermocouple cold end in the meter box. PT1000 is used for measuring the temperature in the cabinet To the Tc is the temperature outside the meter box.
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