Measuring temperature of optical fibre drawing tower furnace

Temperature Measurement

December 2001 Temperature Measurement

Land Instruments, represented by Protea Automation Solutions, are specialists in the field of high temperature measurement and control. In the manufacture of fibre-optic cable, in order to draw high quality low-loss optical fibre with the required strength and attenuation, the temperature of the drawing tower furnace must be stable and precisely controlled. Graphite resistance and induction-heated zirconia furnaces operating at high temperatures, typically 22 000°C, make contact methods of temperature measurement impractical.

Land Instruments solve the problem with its model DDT drawing tower thermometer, with an operating range of 800 to 2600°C. The target, with a measurement spot of 4 mm across at the focus distance of 450 mm, and sensor are interconnected by approximately 2 m of fibre-optic cable.

The thermometer requires a small target size to view between the coils in an induction-heated furnace, or sight down a narrow tube on to the zirconia susceptor. In the case of a graphite resistance type furnace the thermometer has to sight through a quartz window, down through a narrow tube on to the heating element.

Experience has shown outstanding benefits are to be had by using short wavelength thermometers for this application in order to achieve maximum accuracy. A silicon cell detector gives high stability, rapid response and high rate of change of output with temperature. The thermometer provides high-level signal to noise output of 4 to 20 mA for retransmission to a readout or control system.

Protea Automation Solutions

(011) 719 5700

[email protected]

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Temperature Measurement

Measuring temperature of optical fibre drawing tower furnace

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