ラコステ重力計用自動読取装置

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タイトル別名
  • Data Processing System for LaCoste & Romberg Gravimeter
  • ラコステ ジュウリョクケイヨウ ジドウ ヨミトリ ソウチ

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The high resolution and good linearity of the readout system of the LaCoste & Romberg gravimeter justify both a better method for setting the beam position and a better measuring procedure than those described in the manufacturer's instruction manual. The effects of hysteresis following unclamping are reduced if the tilt angle in the direction of the long level is increased, so long as the beam remains horizontal. Moreover, the remaining effects are eliminated by our reading procedure. In this procedure, the output voltage corresponding to the beam position, with a dial setting which does not correspond to the null position, is recorded one minute after unclamping. The dial setting is then changed to bring the beam to the other side of null and the beam position voltage is again recorded one minute later. Finally, the dial is returned to its first position and, after one minute, the beam position is again recorded. The null dial setting can then be determined by interpolation. A new data processing system has been developed to implement the above procedure; this system can also be used for tidal observations. The analog signal from the beam position readout is digitized with an adjustable sampling interval. 101 consecutive digitized values are filtered using a digital low pass filter with trigonometric weights designed by Akaike; this filter has no phase lagg which is an advantage for recording the tides. Its purpose in both field and tidal measurements is to eliminate the effect of microseisms. The following features make the system suitable for field use :1) it is battery operated and has a digital printer.2) all the necessary computations are performed by a built-in microprocesser.3) the print-out includes the environmental factors of temperature, air pressure and level of background vibrational noise. For tidal observations, the system has a D/A converter so that the filtered output can be monitored with a chart recorder. Tests have shown the system to work well both for field gravity measurements and for tidal observations.

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