آزمايش كاليبره كردن نسبي حسگرهاي سرعت سنج CMG-6TD بر روي ميز لرزان با استفاده از نرم افزار SCREAM

Calibration of CMG-6TD Seismometers Using Shaking Table and SCREAM Software

The Dynamic calibration of seismometers establishes the knowledge of the relationship between its input and output and is a prerequisite for reconstruction of the recorded vibrations. The present paper is mainly concerned with the mechanical calibration of the CMG-6TD sensors on the shaking table and the SCREAM software. For the laboratory calibration test, 6 Seismometers were aligned side-by-side on the shaking table. By adjusting the vibration amplitude and frequency of the table at specific values between 0.005-5mm and 30-0.2Hz respectively, the steady state vibrations of the table at each step were recorded simultaneously. In order to measure the response of the table to the applied displacement and frequency of excitation, 5 external accelerometers were installed on the sides of the table. By transforming the recorded acceleration or velocity time histories into displacement (using integration techniques) and comparing the time history and spectral amplitude of recorded and input vibrations, the correction factor for each sensor was evaluated. In the second method, a fixed sinusoidal calibration signal was injected into the calibration coil of 15 instruments. By measuring the peak to peak velocity output (in counts) and calculating back to the equivalent input velocity, the sensitivity of each seismometer was calculated. Totally, the calibration tests indicated that the differences in spectrum amplitudes of the sensors are limited to 5.5%, whereas there is no meaningful difference in frequency contents of the recorded signals.