A Persoz pendulum is a device used for measuring hardness of materials. The instrument consists of a

pendulum A pendulum is a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced sideways from its resting, equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the ...

which is free to swing on two balls resting on a coated test panel. The pendulum hardness test is based on the principle that the

amplitude The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of amplit ...

of the pendulum's

oscillation Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...

will decrease more quickly when supported on a softer surface. The hardness of any given coating is given by the number of oscillations made by the pendulum within the specified limits of amplitude determined by accurately positioned photo sensors. An electronic counter records the number of swings made by the pendulum

Construction

The pendulum consists of balls which rest on the coating under test and form the

fulcrum A fulcrum is the support about which a lever pivots. Fulcrum may also refer to: Companies and organizations * Fulcrum (Anglican think tank), a Church of England think tank * Fulcrum Press, a British publisher of poetry * Fulcrum Wheels, a bicy ...

. The Persoz pendulum is very similar to the Konig pendulum. Both employ the same principle, that is the softer the coating the more the pendulum oscillations are damped and the shorter the time needed for the amplitude of oscillation to be reduced by a specified amount. The two pendulums differ in shape, mass and oscillation time, and there is no general relationship between the results obtained using the two pieces of equipment. In either case, the test simply involves noting the time in seconds for the amplitude of swing to decrease from either 6 to 3 degrees (Konig pendulum) or 12 to 4 degrees (Persoz pendulum).PRA. Mechanical Properties. Accessed: May 6, 2015.

References

{{reflist Hardness instruments Materials science Pendulums Coatings