Actuator
A
device that is controlled by commands that are outputs from
the control computer. Typical examples of actuators are the
fuel injector, anti-lock braking modulator, and exhaust gas recirculation valve.
The simple moving flap type of air flow sensor makes use of
a potential divider that interprets air flow as a voltage.
The wiper of the potential divider is fixed to the spindle
of the sensor. When the flap moves in response to changes
in air flow, the wiper moves along the resistance strip. The
voltage that is transmitted to the control computer is an
exaction representation of air flow.
The petrol injector is an electromagnetic actuator that operates
in a way similar to the action of a solenoid. Current to the
injector is supplied via a relay and the control computer
switches the power transistor on, so that the injector is
operated. The duration of the injection period determines
the amount of fuel that is injected into the engine. The duration
of the injection period (and thus the amount of fuel injected)
is determined by the computer program, which makes use of
the input from the air flow sensor and from other sensors
for throttle position, engine speed, and engine coolant temperature,
for example.
See also sensor.
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