seismometer

https://www.azosensors.com/article.aspx?ArticleID=7

seismometer dan seismograf adalah identik, mereka adalah instrumen untuk merekam gerakan bumi yang terkait dengan gempa bumi, letusan gunung berapi, atau sumber gempa lain seperti ledakan. Seismograf merupakan alat yang menggabungan deteksi dan perekaman dalam satu instrumen.

petikan : https://www.pinterpandai.com/alat-untuk-mengukur-gempa-bumi-disebut/

 souurce: http://www.gcse.com/waves/seismometers.htm

Source: https://www.inquietonotizie.it/wp-content/uploads/2012/02/sismografo-400x3002.jpg

https://socratic.org/questions/590f19137c0149155cd33f90

seismograph

A seismograph, or seismometer, is an instrument used to detect and record earthquakes. Generally, it consists of a mass attached to a fixed base. 

During an earthquake, the base moves and the mass does not. The motion of the base with respect to the mass is commonly transformed into an electrical voltage. The electrical voltage is recorded on paper, magnetic tape, or another recording medium. This record is proportional to the motion of the seismometer mass relative to the earth, but it can be mathematically converted to a record of the absolute motion of the ground. 

Seismograph generally refers to the seismometer and its recording device as a single unit.

(sources:https://earthquake.usgs.gov/learn/glossary/?term=seismograph)

Other resources:

https://www.iris.edu/hq/files/programs/education_and_outreach/aotm/8/Seismograph_Background.pdf

http://www.gcse.com/waves/seismometers.htm