The Development of Active Thermocouples for Diesel Exhaust Temperature Measurement

A family of active thermocouples was developed for high temperature exhaust gas temperature measurement. A combination of thermocouple material improvements, package design and integral signal conditioning vastly improve accuracy and durability performance for diesel emission control. Sensors were developed to withstand temperatures from -40 to +1200°C and vibration levels of 30 G_RMS with immersion lengths over 85mm. Signal conditioning supplies an interface to engine control units and provides an accuracy of up to ±1% from 500 to 1000°C, depending on output type and sensor construction. Results are presented for accuracy, vibration, high temperature stability and time response. System accuracy factors are discussed for various output types.