Does the packaging tube itself carry heat away from the measurement point? How is this corrected?
Yes, the packaging tube in a fiber optic temperature sensor can indeed conduct heat away from or towards the Fiber Bragg Grating (FBG) measurement point. This phenomenon is known as heat conduction and can influence the accuracy of the temperature measurement, especially when there are significant temperature gradients along the sensor or within the measured object.
This effect is primarily managed through careful sensor design and material selection. For instance, OFSCN addresses this in its FBG temperature sensors by:
- Material Selection: Utilizing materials for the encapsulation tube, such as stainless steel or ceramic, chosen for their thermal conductivity properties suitable for the intended temperature range and application.
- Optimized Geometry: Designing the tube with specific diameters and wall thicknesses (e.g., default 0.9mm outer diameter for many FBG temperature sensors, with options for smaller diameters like 0.5mm or 0.6mm) to minimize thermal mass and the cross-sectional area for heat transfer, thereby reducing the impact of conduction.
- Encapsulation Techniques: Employing methods like single-layer or multi-layer seamless tube encapsulation to create a robust yet thermally considered package. For example, ceramic encapsulation can also offer insulation properties in certain applications.
While the packaging tube’s design minimizes these effects, in scenarios with steep temperature gradients, proper installation and thermal contact with the measurement target are crucial.
Here are some of OFSCN’s packaged FBG temperature sensors:
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