Amplitude response of a telemetered seismic system from seismometers to digital acquisition system

Abstract

Automated amplitude response of the complete seismometer, telemetry and recording system js obtaiued trom sinusoidal inputs to the calibration coil. Custom-built software was designed to perform fully automatic cali- bration analyses of the digital signals. In this paper we describe the signals used for calibration and interactive and batch procedures designed to obtain calibration functions in automatic mode. By using a steady-state method we reach a high degree of accuracy in the determination of both the frequency and amplitude of the \ignal. The only parameters required by this procedure are the seismometer mass, the calibration-coil constant and the intensity of the current injected into the calibration coil. This procedure is applicable to telemetered seismic systems and represents an optimization of the processing time. The software was designed to requjre no modification" jf the device used to generate the sinusoidal current should change. In particular, it is possi- ble to changc the number of monotrequcncy packages transmitted to the calibration coil with the on]y restric- tion that the difference between the frequency of two consecutjve packages be greater than 5%; for these rea- sons the procedure is expected to be usefu] for the seismological community. The paper inc]udes a generaI de- scription of thc designing criteria, and of the hardware and software architecture, as well as an account of thc system's performancc during a two year period of operation.