Analysis of Thermocouple Temperature Response under Actual Vehicle Test Conditions

Automotive thermal protection is one of the key areas in the vehicle development process. Critical decisions are usually based on temperature measurement during vehicle testing. Thermocouples are most widely used to determine the temperature of each component during specific test cycle. Therefore, the reliability and accuracy of the thermocouple measurements are of significant importance to the design and release engineers. Errors associated with temperature measurements of automotive components may be caused by radiation from exhaust surfaces such as exhaust manifold, catalytic converter, muffler or exhaust pipes. Other sources of error may be caused by the effect of ambient temperature or airflow if thermocouples are not properly installed. Several errors could arise from the attachment method of the thermocouple to the component or material of interest. These errors affect the thermocouple response to transient changes in test conditions and will also impact the steady state temperature measurement.

This paper presents both analytical results and test data related to the thermocouple response to changes in test conditions such as vehicle speed or exhaust temperature. An estimate of the associated errors in the measured component temperature is determined for different driving conditions.