Design of High Precision Temperature Measurement Circuit for Online Combustion Ion Chromatograph
The on-line combustion ion chromatograph combines sample pretreatment and detection process,which greatly im-proves the detection efficiency.However,too high combustion temperature can reduce the service life of the combustion tube,and too low combustion temperature can cause insufficient sample cracking.Therefore,it is necessary to design a high-precision tem-perature measurement circuit to measure the combustion temperature.Firstly,the RFI filter circuit was designed to suppress the influence of high frequency noise on the thermocouple output thermoelectric power.Secondly,a dual ADC adaptive acquisition cir-cuit was designed to realize the fast switching of the gear.Finally,the Pt1000 temperature measurement circuit was designed to measure the temperature of the cold end,so that the compensation error of the cold end was less than 0.052℃.An equal-preci-sion least squares fitting correction algorithm was proposed.According to the temperature measurement accuracy,the equal-preci-sion interval was automatically divided within the temperature measurement range,which improved the temperature measurement accuracy and reduced the workload of the MCU.The experimental results show that the temperature measurement accuracy can reach 0.6℃in the range of 0～1 200℃.
RFI filteringdual ADC adaptive acquisitionPt1000equal precision least square method
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