A centrifugal governor is a specific type of governor

Governor (device)

A governor, or speed limiter, is a device used to measure and regulate the speed of a machine, such as an engine. A classic example is the centrifugal governor, also known as the Watt or fly-ball governor, which uses a rotating assembly of weights mounted on arms to determine how fast the engine...

 that controls the speed

Speed

In kinematics, the speed of an object is the magnitude of its velocity ; it is thus a scalar quantity. The average speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as...

 of an engine

Engine

An engine or motor is a machine designed to convert energy into useful mechanical motion. Heat engines, including internal combustion engines and external combustion engines burn a fuel to create heat which is then used to create motion...

 by regulating the amount of fuel

Fuel

Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...

 (or working fluid

Working fluid

A working fluid is a pressurized gas or liquid that actuates a machine. Examples include steam in a steam engine, air in a hot air engine and hydraulic fluid in a hydraulic motor or hydraulic cylinder...

) admitted, so as to maintain a near constant speed whatever the load

Load

Load may refer to:*Structural load, forces which are applied to a structure*Cargo*The load of a mutual fund *The genetic load of a population*The parasite load of an organism...

 or fuel supply conditions. It uses the principle of proportional control

Proportional control

A proportional control system is a type of linear feedback control system. Two classic mechanical examples are the toilet bowl float proportioning valve and the fly-ball governor....

.

It is most obviously seen on steam engine

Steam engine

A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

s where it regulates the admission of steam into the cylinder

Cylinder (engine)

A cylinder is the central working part of a reciprocating engine or pump, the space in which a piston travels. Multiple cylinders are commonly arranged side by side in a bank, or engine block, which is typically cast from aluminum or cast iron before receiving precision machine work...

(s). It is also found on internal combustion engine

Internal combustion engine

The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

s and variously fueled turbine

Turbine

A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they move and...

s, and in some modern striking clock

Striking clock

A striking clock is a clock that sounds the hours audibly on a bell or gong. In 12 hour striking, used most commonly in striking clocks today, the clock strikes once at 1 AM, twice at 2 AM, continuing in this way up to twelve times at 12 noon, then starts over, striking once at 1 PM, twice at 2...

s.
The device shown is from a steam engine.