Pendelgravimeters

Pendelgravimeters are instruments used to measure the Earth's gravitational field with high precision. They operate on the principle of a pendulum, where the period of oscillation is influenced by the local gravity. The basic design consists of a pendulum suspended from a fixed point, with a mechanism to measure the time it takes for the pendulum to swing back and forth.

The most common type of pendelgravimeter is the LaCoste-Romberg gravimeter, which was developed in the 1930s. It features a pendulum with a mass at the end, suspended by a fine wire. The period of the pendulum is measured using a quartz clock, and the instrument is designed to be insensitive to temperature changes and other environmental factors.

Pendelgravimeters are used in various fields, including geophysics, geodesy, and oil and gas exploration. They are particularly useful for detecting small changes in the Earth's gravitational field, which can be indicative of subsurface structures or mass movements. The measurements are typically expressed in units of milligals (mGal), where 1 mGal is equal to 10^-5 m/s^2.

Modern pendelgravimeters have improved sensitivity and accuracy, thanks to advancements in sensor technology and data processing. They are often used in conjunction with other geophysical methods to provide a more comprehensive understanding of the subsurface. Despite their historical significance, pendelgravimeters are gradually being replaced by more advanced technologies such as superconducting gravimeters and absolute gravimeters.