Kater's pendulum
（重定向自Kater pendulum）
![Kater's original pendulum, showing use, from Kater's 1818 paper. The pendulum's period was timed by comparing its swing with the pendulum in the precision clock behind it. The sight (left) was used to avoid parallax error.](/Images/godic/202501/22/Kater_pendulum_use0618.png")
![A Kater's pendulum and stand](/Images/godic/202501/22/PenduloCaminos0618.jpg")
![Drawing of Kater's pendulum (a) opposing knife edge pivots from which pendulum is suspended (b) fine adjustment weight moved by adjusting screw (c) coarse adjustment weight clamped to rod by setscrew(d) bob (e) pointers for reading](/Images/godic/202501/22/Kater_pendulum0618.png")
![Gravimeter with variant of Repsold pendulum](/Images/godic/202501/22/Repsold0618.jpg")
A Kater's pendulum is a reversible freeswinging pendulum invented by British physicist and army captain Henry Kater in 1817 for use as a gravimeter instrument to measure the local acceleration of gravity. Its advantage is that, unlike previous pendulum gravimeters, the pendulum's centre of gravity and center of oscillation don't have to be determined, allowing greater accuracy. For about a century, until the 1930s, Kater's pendulum and its various refinements remained the standard method for measuring the strength of the Earth's gravity during geodetic surveys. It is now used only for demonstrating pendulum principles.