Application of communication network theory to the electromagnetic seismograph

1964 ◽  
Vol 54 (5A) ◽  
pp. 1479-1489
Author(s):  
S. Dopp
Keyword(s):  
Communication Network ◽  
Transfer Function ◽  
Equivalent Circuit ◽  
Network Theory ◽  
Band Pass Filter ◽  
Pass Filter ◽  
Electromagnetic Seismograph ◽  
Band Pass

Abstract Communication network theory is applied to the equivalent circuit of the electromagnetic seismograph. The seismograph's transfer function is derived in the general case of an arbitrary linear passive coupling network between pendulum and galvanometer. Examples are given, one of which refers to the construction of a band-pass filter in the form of a lattice of filter galvanometers.

Magnification curves of electromagnetic seismographs

1964 ◽  
Vol 54 (5A) ◽  
pp. 1459-1471
Author(s):  
S. K. Chakrabarty ◽  
G. C. Choudhury ◽  
S. N. Roy Choudhury
Keyword(s):  
General Solution ◽  
Frequency Response ◽  
Experimental Method ◽  
Phase Shifts ◽  
Response Curves ◽  
Operating Condition ◽  
Coil Inductance ◽  
The World ◽  
Electromagnetic Seismograph ◽  
Proper Design

Abstract The general solution of the equations connecting the motion of the two coupled components in an electromagnetic seismograph has been obtained in another paper and it shows that the magnification of a seismograph depend on seven instrumental constants. Using these results, equations and curves have been derived in the present paper from which the Magnification as well as Phase shifts in the response of a seismograph and their variations with damping and coil inductance can be easily obtained. Based on these curves a number of magnification curves for different combinations, which are in operation at the different seismological stations of the world, have been derived. Suitable equations and curves have also been obtained which can be used for estimating the absolute Magnification of a Seismograph. An experimental method of obtaining the frequency response curves of seismographs in their operating condition has been described and the results obtained by this method has been given. It has been indicated how the results incorporated in the present paper can be used in the proper design of seismographs required for the different purposes.

Response characteristics of electromagnetic seismographs and their dependence on the instrumental constants

1949 ◽  
Vol 39 (3) ◽  
pp. 205-218
Author(s):  
S. K. Chakrabarty
Keyword(s):  
General Solution ◽  
Equation Of Motion ◽  
Harmonic Motion ◽  
Response Characteristics ◽  
Local Earthquakes ◽  
Simple Harmonic Motion ◽  
The Earth ◽  
Electromagnetic Seismograph ◽  
Different Types ◽  
Proper Values

Summary The equation of motion of the seismometer and the galvanometer in an electromagnetic seismograph has been derived in the most general form taking into consideration all the forces acting on the system except that produced by hysteresis. A general solution has been derived assuming that the earth or the seismometer frame is subjected to a sustained simple harmonic motion, and expressions for both the transient and the steady term in the solution have been given. The results for the particular case when the seismograph satisfies the Galitzin conditions can easily be deduced from the results given in the present paper. The results can now be used to study the response characteristics of all electromagnetic seismographs, whether they satisfy the Galitzin conditions or not, and will thus give an accurate theoretical picture of the response also of seismographs used for the study of “local earthquakes” and “microseisms” which do not in general obey the Galitzin conditions. The results obtained can also be used to get analytically the response of the seismographs for different types of earth motion from the very beginning, and not only after the transient term has disappeared. The theory of the response to simple tests used to determine the dynamic magnification of any seismograph and also to determine and check regularly the instrumental constants of the seismographs has been worked out. The results obtained can also be used for ascertaining the proper values of the instrumental constants suitable for the various purposes for which the seismographs are to be used.

An integral solution of the electromagnetic seismograph equation

1960 ◽  
Vol 50 (3) ◽  
pp. 461-465
Author(s):  
R. E. Ingram
Keyword(s):  
Differential Equation ◽  
Green’S Function ◽  
Green's Function ◽  
Integral Solution ◽  
Ground Movement ◽  
Ground Movements ◽  
Angular Movement ◽  
Electromagnetic Seismograph

ABSTRACT In investigating the response of an electromagnetic seismograph to various ground movements it is advantageous to have the solution of the differential equation as an integral. This is done by finding the Green's function, f(s), for the particular instrument. The angular movement of the galvanometer is then θ(t)=q∫0tf(s)x″(t−s)ds where x(t) is the ground movement and prime stands for the operator d/dt. It is sufficient to find one function, F(s), with dF/ds = f(s), to give the response to a displacement test, a tapping test, or a ground movement.

Benndorf's formula for the dynamic magnification of an electromagnetic seismograph

1969 ◽  
Vol 59 (4) ◽  
pp. 1713-1717
Author(s):  
G. A. Bollinger
Keyword(s):  
Steady State ◽  
Natural Frequencies ◽  
At Resonance ◽  
Velocity Sensitivity ◽  
Electromagnetic Seismograph ◽  
Dynamic Velocity

Abstract The indicator equation for a seismogram from an electromagnetic seismograph is integrated under the assumption that the trace has the form of a suddenly beginning sinusoid. An expression for the velocity sensitivity is derived from the integrated result and applied to the particular case of a seismometer-galvanometer combination with natural frequencies of 2 Hertz-200 Hertz respectively. For that seismograph the dynamic velocity sensitivity at transducer—earth resonance is one-fifth of the steady-state harmonic sensitivity at resonance.

A note on the calibration of the electromagnetic seismograph

1973 ◽  
Vol 63 (3) ◽  
pp. 1145-1155
Author(s):  
Hans Jarosch ◽  
A. R. Curtis
Keyword(s):  
Time Domain ◽  
Initial Conditions ◽  
System Parameters ◽  
Electromagnetic Seismograph ◽  
The Time Domain ◽  
Explicit Expressions

abstract Explicit expressions are given for the response in the time domain of a zerocoupled seismometer-galvanometer combination for a step of acceleration as initial conditions. The results may be directly applied for computing the system parameters.

A rapid method for calibrating Willmore seismographs

1964 ◽  
Vol 54 (5A) ◽  
pp. 1473-1477
Author(s):  
K. G. Barr
Keyword(s):  
Rapid Method ◽  
Velocity Sensitivity ◽  
Electromagnetic Seismograph

Abstract A method is described for calibrating Willmore seismographs. It could be applied to any other electromagnetic seismograph having a galvanometer period substantially shorter than the seismometer period. The method is rapid and involves very little equipment. An overall accuracy of 20% in the velocity sensitivity is easily attainable.

The Development of Ancient Earthquake Instruments

2006 ◽  
Author(s):  
Hong-Sen Yan ◽  
Kuo-Hung Hsiao
Keyword(s):  
Great Sensitivity ◽  
Recording System ◽  
Major Difficulty ◽  
Ancient China ◽  
Sensing Element ◽  
Pendulum System ◽  
Timing System ◽  
Electromagnetic Seismograph ◽  
Zhang Heng ◽  
Made In

This paper studies sensing element designs in ancient seismometers and describes the developments of ancient earthquake instruments. A basic seismograph comprises a seismometer, a recording system, and a timing system. The major difficulty in the development of a seismograph was the design of the seismometer. And, the break through was the use of a pendulum system as a sensing element that responded to ground motion and did not move with the ground. Early seismoscopes were primarily intended to determine that an earthquake had happened. The first seismoscope invented by Zhang Heng was Hou Feng Di Dong Yi made in ancient China around the year 132 AD. The truly successful seismographs were first designed and built in the 1880s by a group of British scientists in Japan. In 1906, Boris Galitzin developed a working electromagnetic seismograph with a great sensitivity. Finally, a comparison with the recording systems of ancient seismographs is concluded.

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