Browsing by Author "Tomberg, Teemu"
Now showing 1 - 2 of 2
- Results Per Page
- Sort Options
- 88Sr+-ionikellon magneettinen suojaus
Sähkötekniikan korkeakoulu | Bachelor's thesis(2014-05-11) Tomberg, Teemu - Laser-Based Thermometry over Long Distances
Sähkötekniikan korkeakoulu | Master's thesis(2016-02-15) Tomberg, TeemuElectronic distance meters are routinely used in many long-distance applications to accurately determine the distance between two points. Currently, the instruments are reaching towards relative uncertainties of 10^-7, the main obstacle being the uncertainty in the refractive index of air. The refractive index is conventionally calculated from the meteorological observations of the ambient air using either Edlen or Ciddor equations. However, the accuracy of these equations is often limited by inaccuracy in the integral meteorological observations. Temperature, which has to be known at ~100 mK level, is by far the most significant uncertainty source in many advanced distance measurements making accurate temperature meters a key for improving the quality of modern ranging instruments. A solution is to use laser absorption spectroscopy for non-invasive measuring of the average temperature of air between the two points of interest. In this thesis, a laser-based thermometer is constructed for accurate determination of the refractive index of air over long distances. The thermometer, which is based on direct absorption spectroscopy of oxygen transition near 770 nm, is demonstrated for the first time in real field conditions up to 864 m in distance in a typical distance measurement configuration. The results prove that the instrument can achieve RMS noise well below 100 mK and accuracy of +/-300 mK using 120 s measurement time, which is to our knowledge the best reported resolution for such a long distance.