Evaluating thermal concerns is often addressed during the automotive lamp design process. The thermocouple device is used frequently for temperature measurements to locate and quantify hot spots that arise in the automotive lamp assembly. This study seeks to review the techniques used for thermocouple temperature measurement. Common techniques are described in detail and evaluated. An experiment coupled with computer simulation is introduced and performed that tests accuracy and compares the methodology and results of the different thermocouple measurement techniques. The technique that most directly measures both inside (exposed to light source) and outside (away from light source) surface temperature is demonstrated to have advantages. Correlation to heat deflection temperature and thermal damage such as warp and metalization blemish (haze) is described. Lamp thermal measurement techniques, using thermocouples, are varied and the accuracy has been disputed for years. Questions often arise regarding the absolute temperature on the lamp. More importantly is that the measurement technique must be repeatable and correlated to lamp failure mode. Developing an accurate measurement technique should remain a priority for lamp temperature measurement. Results from the theory and data given in the paper show real performance benefits when certain best practices are used with thermocouples. These best practices include: 1) use small wire thermocouples, 30 gauge or higher gauge size, 2) always route the thermocouple lead along the surface to be measured, minimizing the thermal gradient in the wire and heat flux from the thermocouple junction, 3) use a thermal interface material (such as thermal grease) to reduce the thermal resistance between the plastic and the thermocouple junction, 4) use a thermal grease on an inside surface to eliminate the illumination error effect. Consistently following these best practices will result in the best prediction of warp and blemish on an automotive lamp.
Evaluating thermocouple measurement techniques for automotive lighting
Bewertung von Messtechniken für die Kfz-Beleuchtung mit Thermoelementen
2004
6 Seiten, 10 Bilder, 2 Tabellen, 2 Quellen
Conference paper
English
Evaluating thermocouple measurement techniques for automotive lighting
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