Sensores Y Actuadores Informacion En Ingles

SENSORS & ACTUATORS

SENSORS AND ACTUATORS
Computer controlled systems continually
monitor the operating condition of today's
vehicles. Through sensors, computers
receive vital information about a number of
conditions, allowing minor adjustments to be
made far more quickly and accurately than
mechanical systems. Sensors convert
temperature, pressure, speed, position and
other data intoeither digital or analog
electrical signals.

A digital signal is a voltage signal that is
either on or off with nothing in between. A
switch is the simplest type of digital signal
sensor. The signal from the switch could be
0 volts when off and 12 volts when on. Analog
signals on the other hand have continuously
variable voltage. A good example is the
coolant temperature sensor. Thecoolant
temperature sensor may vary the voltage
signal anywhere between 0 volts and 5 volts
depending on the temperature of the engine.

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SENSORS & ACTUATORS
The digital signal is the easiest for the
computer to understand because it reads the
signal as either "on" or "off." The analog
signal must be conditioned orconverted to
digital so the computer can understand it.
(This will be covered later.)
While a vehicle may have many different
sensors, there are three main categories:
voltage-generating, resistive and switches. A
voltage-generating sensor generates its own
voltage signal in relation to the mechanical
condition it monitors. This signal in turn
relays to the computer data about the
condition ofthe system it controls. A resistive
sensor reacts to changes in mechanical
conditions through changes in its resistance.
The computer supplies a regulated voltage
or reference voltage to the sensor and
measures the voltage drop across the
sensor to determine the data.
Switch sensors toggle a voltage from the
computer high or low, or supply an "on" or
"off" voltage signal to the computer.This type
of sensor may be as simple as a switch on
the brake pedal or as complex as a
phototransistor speed sensor.
The computer uses the sensor data to
control different systems on a vehicle
through the use of actuators. An actuator is
an electromechanical device such as a relay,
solenoid or motor. Actuators can adjust
engine idle speed, change suspension
height or regulate the fuelmetered into the
engine.
This chapter describes several specific
sensors used in automobiles, such as
potentiometers, thermistors and
phototransistor / LED combinations. This
chapter also addresses actuators that
complete the control process by carrying out
the computer's instructions.

The Sensors and Actuators section is divided
into the following areas:
Resistive sensors:potentiometers
thermistors
piezo resistive
Voltage generating sensors:
piezo electric
zirconia-dioxide
magnetic inductance
Switch sensors:
phototransistors and LEDs
speed sensors
G-sensors (Air Bag Impact Sensors)
Actuators:
stepper motors
solenoids
RESISTIVE SENSORS
Potentiometers
A potentiometer is a variable resistor that is
commonly used as a sensor. A
potentiometer has threeterminals: one for
power input, one for a ground and one to
provide a variable voltage output. A
potentiometer is a mechanical device whose
resistance can be varied by the position of
the movable contact on a fixed resistor. The
movable contact slides across the resistor to
vary the resistance and as a result varies the
voltage output of the potentiometer. The
output becomes higher or lowerdepending
on whether the movable contact is near the
resistor's supply end or ground end.

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© Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.

SENSORS & ACTUATORS
Thermistors

The vane type air flow meter on an EFI
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