AN ANALYSIS OF FACTORS LIMITING SEISMIC DETECTOR SENSITIVITY.
Final rept., 16 Oct 64-15 Jan 66,
DAVID SARNOFF RESEARCH CENTER PRINCETON N J
Pagination or Media Count:
A detailed analysis is presented to show the effect of certain design parameters on the signal-to-noise ratios of systems in which seismometers are coupled to galvanometer amplifiers. General guidelines are presented for optimizing the signal-to-noise ratio of such systems. The effect of feedback on the signalto-noise ratio of seismic detector systems is analyzed. It is shown that if the amplifier input resistance is much higher than the required external damping resistance for a given seismometer transducer, the use of feedback to reduce the amplifier input resistance provides better signal-to-noise ratio than the use of a shunt resistance at the amplifier input terminals. It is also shown that feedback should not be used to increase the amplifier input resistance in order to provide proper damping. The potential advantage of displacement transducers over velocity transducers at lower frequencies is discussed. It is contended that the displacement transducer can have no advantage at frequency for which the sensitivity of the velocity transducer system is limited by the thermal noise of the amplifier input resistance. The lowest useful frequency for the velocity transducer system is determined in practice by the 1f noise of the amplifier. The sensitivity of clusters of seismometers connected to a single amplifier is summarized briefly and noise measurements on the Texas Instruments RA-3 Parametric Amplifier are presented. Author
- Seismic Detection and Detectors