Seismograph 11
Seismograph 11 :
An instrument that allows recording to be made of the earth's oscillations caused by the passage of seismic waves. In schematic terms, a seismograph comprises a weight, with a motor pen at one end, suspended by a spring on a support fixed to the ground, on which is fixed a roll of paper that scrolls continuously. When the ground sways, the support moves as well as does the roll of paper, while the weight acts like a pendulum and stays still, allowing the pen to record the earthquake by drawing oscillations on the paper (seismogram). In modern seismographs, the pen and the roll of paper have been replaced by a digital system for recording electrical signals transmitted by an electromagnet sensor placed inside a seismometer attached to the ground
