4 - 1 Seismograph

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Seismograph is an instrument which gauges ground tremors.
Recent seismograph is made up of a sensor module called seismoscope and a recording device which consists of an amplifier and a recorder, shown as Figure 1.
Seismoscope converts tremors into a series of electric signals by moving a coil attached on the tip of a pendulum in a magnetic filed, as shown Figure 2. A set of three seismoscopes is necessary to measure up-down, east-west and north-south components of the tremors
The recording device receives, amplifies and finally records a series of electric signals from the seismoscope. The recording methods are varied. In old days, tremors were directly recorded by a pen on a paper rolled on a cylindrical drum. Nowadays, we mainly use computer assisted digital recorders.

Figure 1. Components of seismograph

Figure 2. Sensor module of seismograph (up-down seismoscope)

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