Understanding the Challenges of Aluminum Wire Temperature Measurement
Aluminum Wire Temperature Measurement presents unique challenges due to the small size of the wire, its movement during production, and the low and variable emissivity of aluminum surfaces. Accurate temperature control is essential for maintaining product quality and process stability in high-speed wire production. In this section, we introduce the key factors affecting measurement accuracy and how to overcome them using non-contact infrared pyrometers.
Watch the Video: Aluminum Wire Temperature Measurement in Action
In-Depth Analysis: Detailed Breakdown of Aluminum Wire Temperature Measurement
Since the aluminum wire diameter is smaller than the pyrometer’s measurement spot—and using a smaller spot is not feasible due to the wire potentially shifting out of the field of view—accurate temperature measurement becomes challenging. In such cases, the effective emissivity is determined by the ratio of the areas:
Effective Emissivity = (Area of the wire) / (Area of the spot)
or, when assuming circular cross-sections:
Effective Emissivity = (Diameter of wire)² / (Diameter of spot)²
This reduced effective emissivity can significantly impact the pyrometer’s ability to detect low temperatures accurately.
- a) when spot Ø10mm, and wire Ø2mm, effective ε=0.25; Real wire surface ε=0.1;
and full measurement emissivity will be E=0.025;
- b) When spot Ø10mm, and wire Ø6mm, effective ε=o.75 ; Real wire surface ε=0.1
and full measurement emissivity will be E=0.075”
It is evident that the pyrometer’s emissivity settings must be adjusted for each specific wire diameter.
Consider a pyrometer with a manufacturer-specified minimum brightness temperature of 105°C:
- If E = 0.025, the minimum measurable temperature will be 210°C.
- If E = 0.075, the minimum measurable temperature will be 170°C.
Measurements may also be affected if the wires are made of different alloys. The situation is likely to be simplest under the following conditions:
- The customer consistently uses the same alloy.
- A fixation wheel is used to prevent wire movement, ensuring that the measurement spot remains stable. As a result, the spot diameter can be less than 10 mm.
