The HTS-1000 sensor enables fiber optic temperature measurements up to 1000 °C. In addition to the traditional benefits of fiber optic sensors, including immunity to electromagnetic interference, better environmental stability and enhanced remote sensing as compared to traditional electronic sensors, the HTS-1000 extends these benefits to ultra-high temperature applications, ranging from turbine engine test and development to refinery process monitoring and control. Microwave environments can be accommodated with an all glass sensor.
The HTS-1000 sensor is used in conjunction with fiber optic interrogators and is now fully integrated with the Micron Optics interrogator, sm125, or the National Instruments equivalent NI PXIe-4844,that we typically use to read out the sensor.
The OSI driver, available from Micron Optics or NI, functions to acquire the optical spectrum and then scale the acquired spectrum into an accurate temperature measurement using Chiral Photonics’ signal processing routines and enables full integration within LabVIEW.
The HTS-1000 is based on Chiral Photonics’ chiral diffraction grating, fabricated by twisting a fiber as it is passed through a miniature heat zone to produce a distinct dip in the transmission spectrum. The spectral position of the dip in this chiral fiber changes with temperature allowing it to be used as a temperature sensor.
Temperature testing was carried out in a computer-controlled high-temperature oven in which the temperature was also monitored by a thermocouple. Both long-term temperature stability and temperature sensitivity were tested using a fiber optic interrogator to monitor sensors as they were cycled from room temperature to 1000 °C. The characteristic spectral dip wavelength shifts to the red by approximately 1.3 nm as the temperature is raised by 100 °C. The figure below shows the wavelength of transmission dip of a chiral fiber versus temperature. The temperature was cycled five times from 700 °C to 1000 °C in the course of 24 hours, dwelling for 3 hours at these temperatures. The inset shows the temperature variations. As seen in the figure below, the HTS-1000 is capable of reliably measuring temperature up to 1000 °C with better than 1% accuracy. Drift measured over more than 1400 hours at 900 °C was 0.0005 °C/hr.