Calibration Of High-Temperature, Fiber-Optic, Microbend, Pressure Transducers

J W Berthold; W L Ghering; D Varshneya

doi:10.1117/12.937510

28 April 1987 Calibration Of High-Temperature, Fiber-Optic, Microbend, Pressure Transducers

J W Berthold, W L Ghering, D Varshneya

Proceedings Volume 0718, Fiber Optic and Laser Sensors IV; (1987) https://doi.org/10.1117/12.937510
Event: Cambridge Symposium-Fiber/LASE '86, 1986, Cambridge, MA, United States

Abstract

We have measured the pressure response of a high-temperature pressure transducer fabricated from fused silica. This transducer uses a microbend fiber-optic sensor to measure diaphragm deflection. The transducer was characterized at pressures up to +690 kPa and tem-peratures to 540°C. The experimental data show approximately a linear dependence on the applied pressure when the microbend sensor is preloaded. This behavior agrees with the calcu-lated results for the linear deflection of a preloaded diaphragm with applied pressure. The experimental results showed a zero offset when the temperature was raised, and also the slope of the pressure response curve decreased with increasing temperature. The observed zero shift to 540°C was 15 times the theoretical predictions. The observed change in slope with temperature was about four times less than the slope at room temperature. These discrepancies have been attributed to the thermally induced radial tensile stress in the fused-silica assembly. These stresses were the result of the original pressure-sealing method that was used for pressure calibration. A modified pressure seal was used to eliminate the thermally induced stresses. Results of the tests performed at various temperatures showed much better agreement of the zero offset and the change in slope of the pressure-response curve with theoretical predictions. The transducer with the original pressure seal was insensitive to vibration over the frequency range from 50 Hz to 2500 Hz. The vibration response was less than 0.25% of the full-scale pressure response. When subjected to three times the design pressure, a permanent offset in the pressure-response curve was observed. This has been attributed to the change in the preload of the clamped fiber.

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J W Berthold, W L Ghering, and D Varshneya "Calibration Of High-Temperature, Fiber-Optic, Microbend, Pressure Transducers", Proc. SPIE 0718, Fiber Optic and Laser Sensors IV, (28 April 1987); https://doi.org/10.1117/12.937510

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