Fiber optic nano temperature sensor
Fiber optic nano temperature sensors belong to a special class of fiber optic sensors . The difference lies in the manufacturing method. Fiber optic temperature sensors usually use specially prepared fiber optic ends. At these fiber ends are z. B. miniaturized English Fabry Perrot Cavities , semiconductor chip made of gallium arsenide (GaAs) with Bragg grating . In the case of fiber optic nano temperature sensors, on the other hand, nanoscale GaAs powder is bound in adhesive and replaces the previous GaAs chip. Due to the light scattering of the particles, the optical response is similar to that of the crystal. This special manufacturing method makes the sensors significantly more robust.
Manufacturing
The gallium arsenide crystals are processed into a powder. The glass fiber required for fiber production is first processed. To do this, the fiber must be stripped, shortened to the desired length and sanded at the fiber end. The end face is then carefully inspected. The fiber end face must be uniform and must not have any cracks, fissures or flaking. Epoxy resin, for example, can be used as the adhesive. The gallium arsenide powder is first dissolved in the adhesive. The fiber end face is then pressed into the adhesive mixture.
Structure & measuring principle
The nano temperature probes consist of a Teflon- coated glass fiber, which is provided with a drop of gallium arsenide at the fiber tip. The sensors are completely non-metallic. GaAs becomes optically transparent from a light wavelength of 850 nm. The position of the strip edge is temperature-dependent and shifts by 0.4 nm / Kelvin. The associated measuring device contains a light source and a device for spectral detection of the position of the strip edge. This allows the temperature to be determined very precisely.
application areas
Medical applications
Temperature measurements in magnetic resonance tomographs are very difficult. There are magnetic flux densities of a few Tesla, and metallic sensors lead to errors in the image acquisition. Nano temperature probes with diameters of 0.5 mm are available for special cancer therapies. These can be used in a minimally invasive way to monitor tissue temperature. Healthy tissue should not be heated above 40 ° Celsius by the action of electromagnetic fields, while carcinogenic tissue is denatured by higher temperatures. Other fields of application for this measurement technology are in laser therapy. Laser energy is coupled in through an endoscope and the temperature at the therapy site is measured with a fiber optic nanoprobe.
Microwaves and RF environments
Chemical digestions under pressure and temperature for the determination of traces and ultra-traces in downstream analysis processes or syntheses under mild conditions are increasingly being carried out in apparatuses heated with microwaves. It was found that under certain pressure and temperature conditions, the yield or efficiency in extraction or digestion processes could be significantly improved. Fiber optic nano temperature sensors are almost the only way to control processes in terms of temperature in microwave chemistry.
Because they offer complete immunity to RF and microwave radiation. Thanks to their special manufacturing process, the sensors are designed to withstand harsh and aggressive environments.
Generator and transformer
To ensure operational safety in electrical networks , operators are increasingly starting to measure the temperature at critical points in turbo generators and power transformers . High power generators are often filled with hydrogen for effective cooling . Fiber optic nano temperature sensors are able to ensure precise temperature measurement in oil-filled transformers.
Individual evidence
- ↑ [1] . Article Nano meets temperature sensor 18 March 2013.
- ↑ [2] . Nano kit for making nano temperature probes March 18, 2013.
- ↑ [3] . Nano temperature sensor March 18, 2013.
- ↑ [4] . Website application fiber optics 15 April 2013.
- ↑ [5] . Website application fiber optics 15 April 2013.
- ↑ Dr. rer. nat. Claus Renschen: Indispensable measuring method. In: 'MSR Magazin 5/2007
- ↑ [6] . Fiber optics website April 15, 2013.