Design and analysis of gas temperature measurement module in motor vehicle exhaust online measurement system

摘要

The mass flow rate of vehicle exhaust significantly influences the measurement of the exhaust pollutants emission factors, meanwhile the exhaust gas temperature measurement is most important in the measurement of exhaust gas mass flow. In order to measure the temperature of exhaust gas accurately and sensitively, a motor vehicle exhaust online measurement experimental system has been developed. The article reports on the design and analysis of gas temperature measurement module in this system. The gas temperature measurement consists of a high-precision K-type thermocouple and a weak signal amplifier circuit. The K-type thermocouple was used to measure the temperature of exhaust gas. Based on the AD595AQ, which was a complete instrumentation amplifier chip with a cold junction compensator for thermocouple, the weak signal of thermocouple was amplified to achieve accurate and rapid measurement of exhaust gas temperature. The real experimental results showed that the detection time is 0.5s, the deviation is+0.2 degrees C, and the detection limit is 573 degrees C. The subsequent analysis showed that the gas temperature measurement module performed well to support the system.