A Doppler ultrasonic flow meter uses a transducer to emit an ultrasonic beam into the stream flowing through the pipe. He stated that the frequencies of the sound waves received by an observer are dependent upon the motion of the source or observer in relation to the source of the sound. The Doppler ultrasonic flow meter operates on the principle of the Doppler Effect (or Doppler shift), which was documented by Austrian physicist and mathematician Christian Johann Doppler in 1842. To obtain accurate measurements, it’s important to know which flow meter to use for your application. The Doppler and transit time flow meters operate on a similar principle, but the technology varies significantly. Both are designed to clamp onto the outside of the pipe wall without breaking the line or interrupting the flow. There are two types of ultrasonic flow meters, Doppler and transit time. The method is not limited to binary stars, but can be applied to any astrophysical configuration in which spectral lines are generated by separate (non-rotational symmetric) regions.Ultrasonic flow meters are non-intrusive devices that use acoustic vibrations (ultrasonic waves) to measure flow rate of liquids. With tachoastrometry, radial velocities and astrometric positions can be measured simultaneously for many double line system binaries in an easy way. This device together with an optimized data analysis will further reduce the measurement errors. The technique can be further improved by using simple devices to simultaneously record the spectra with 180 degrees angles. We compute and provide the function expressing the shift of the centroid of a seeing-limited image in the presence of a narrow slit.Ĭonclusions: The proposed technique is simple to use and our test shows that it is amenable for deriving astrometry with milli-arcsecond accuracy or better, beyond the diffraction limit of the telescope. We describe a simple optical device to simultaneously record pairs of spectra rotated by 180 degrees, thus reducing systematic effects. We measure an astrometric signal in radial velocity of 276 m s -1, which corresponds to a separation between the two components at the time of the observations of 18 ± 2 milli-arcseconds. Results: We use the UVES spectrograph at the VLT to observe the known spectroscopic binary star HD 188088 (HIP 97944), which has a maximum expected separation of 23 milli-arcseconds. The spatial resolution is determined by the precision with which differential radial velocities can be measured. Methods: By using basic concepts of slit spectroscopy we show that the geometry of composite systems can be reliably retrieved by measuring only radial velocity differences taken with different slit angles. Spectra of composite systems (e.g., spectroscopic binaries) contain spatial information that can be retrieved by measuring the radial velocities (i.e., Doppler shifts) of the components in four observations with the slit rotated by 90 degrees in the sky.Īims: We aim at developing a framework to describe the method and to test its capabilities in a real case.
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