Which instrument measures the strain of rock under pressure?

The instrument that measures the strain of rock under pressure is a strain transducer. A strain transducer is specifically designed to detect and measure deformation or strain in materials, including rock, under stress conditions. By converting physical deformation into an electrical signal, strain transducers provide critical data on how rock masses respond to loading, which is essential in geotechnical engineering, mining, and assessing natural hazards.

Seismometers, while crucial for measuring seismic activity, focus on detecting vibrations caused by earthquakes and other seismic events rather than directly measuring strain. Magnetometers are used to measure magnetic fields and are not relevant to assessing strain. Flood gauges monitor water levels and are unrelated to rock strain measurements. Therefore, the strain transducer is the appropriate choice for measuring rock strain under pressure.