Solutions for the correction of temperature measurements based on beaded thermocouples

Thermocouples are a practical and potentially accurate means for determinin g surface temperatures in many applications. Yet, significant errors can of ten arise during the usage of beaded thermocouples because of the effects o f junction displacement, contact resistance, and stray heat transfer to the surrounding environment. To help offset these potentially significant sour ces of errors, Duhamel's integral in Laplace form was first used to relate the response of a surface thermocouple to the true substrate temperature. O nce formulated, both exact and approximate Laplace inversion methods were u sed to derive closed-form corrective solutions. The resulting thermocouple correction curves show good agreement between themselves and existing analy tical expressions and indicate the potentially deleterious effects of junct ion displacement, contact resistance, and the stray heat transfer to the su rrounding environment. (C) 2001 Elsevier Science Ltd. All rights reserved.