Scientists and engineers often use proving rings as a way to measure force. The devices are made using a ring of metal with a spring-like consistency. Inside the ring there is a screw attached to a dial with measurements on it and a plate that vibrates after being struck with something. The contraption in the center works to show the ring's diameter after it has been compressed or stretched, which produces a reliable force measurement that can be used for other purposes.
To use a proving ring, a person will exert force on the ring in some way—generally either pushing from both ends or pulling it apart—and then strike the plate to start vibrations. At this point, the screw is generally turned until it touches the plate and stops it from vibrating. When the vibration stops, the number on the dial will show exactly how much force was used on the ring. The metal used to make the rings is often quite thick, so any flexing will often be very slight, which facilitates the need for precise measurement tools.
Proving rings are often used to calibrate the amount of force used within various force-testing devices. Once the calibration is set, other materials are placed in the devices, and it is possible to see if they can withstand the same force that was being applied to the proving ring. In this way, scientists can determine the exact strengths of various materials.