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TEMPERATURE SENSOR
Temperature Sensor
• Measures air and liquid temperatures between –40 °C
and +130 °C.
• For
proper
amount
of
fuel
injection
Commonly used Automotive Temperature Sensors are:
1.
2.
Coolant
Intake
Temperature
Air
Temperature
(ECT)
(IAT)
Sensor
Sensor
3. Exhaust Recirculation Gas Temperature Sensor
Engine Coolant Temperature (ECT)
Sensor
• Usually located just before the thermostat.
● Responds to change in Engine Coolant
Temperature.
● Critical to many ECM functions such as fuel
injection, ignition timing, variable valve
timing, transmission shifting, etc.
Intake Air Temperature (IAT) Sensor
• ●Detects the temperature of the incoming air
stream.
●On a cold starts, heats up the incoming air.
●On vehicles equipped with a MAP sensor, the
IAT is located in an intake air passage.
● On Mass Air Flow sensor equipped vehicles, the
IAT is part it.
Exhaust Gas Recirculation (EGR)
Temperature Sensor
• The EGR Temperature Sensor is located in the
EGR passage and measures the temperature
of the exhaust gases.
●As the temperature increases, the ECM
opens the EGR valve to
allow the
exhaust gases to flow into the intake manifold.
Thermistors
• If Thermistors are exposed to external heat, their resistance drops
drastically and, provided the supply voltage remains constant, their
input current climbs rapidly. This property is utilized for
temperature measurement.
●It is possible to measure a wide range of liquid temperatures.
● Thermistors comprised of metal oxides and oxidized mixed
crystals.
●This mixture is produced by sintering and pressing with the
addition of binding agents.
ECT, IAT, & EGR Temperature Sensor
Operation:
• As the temperature increases, the voltage signal decreases.
●The decrease in the voltage signal is caused by the decrease
in resistance. The change in resistance causes the voltage
signal to drop.
●When the sensor is cold, the resistance of the sensor is high,
and the
voltage signal is high.
●As the sensor warms up, the resistance drops and voltage
signal
decreases.
●From the voltage signal, the ECM can determine the
temperature of the coolant, intake air, or exhaust gas
temperature
PRESSURE SENSOR
PRESSURE SENSOR
Pressure sensor
• Application : Engine management
• Function : Barometric pressure measurement
• Installation : Printed circuit board (PCB)
• Sensing principle : Silicon micromechanics with integrated evaluation circuit
Low-pressure sensors for gaseous media
•
Application :Engine management
•
Function Registration of intake-manifold pressure or atmospheric pressure Installation Air-intake tract
•
Sensing principle: Micromechanics with piezoresistive sensor element (MEMS based)
HUMIDITY SENSOR
• Sometimes, after rains, the air feels moist. The
water seems to have suspended in the air.
However, in certain AC’s you click some
buttons and the atmosphere brightens up.
How and why does it all happen? Moisture
forms up in the air, resulting in humidity.
However, the humidity sensor in your AC picks
it up and cleans it up for you. Isn’t that
wonderful? Let’s take a look how it does that.
• A humidity sensor (or hygrometer) senses,
measures and reports both moisture and air
temperature. The ratio of moisture in the air
to the highest amount of moisture at a
particular air temperature is called relative
humidity. Relative humidity becomes an
important factor, when looking for comfort
• Humidity sensors work by detecting changes that alter
electrical currents or temperature in the air. There are
three basic types of humidity sensors: capacitive,
resistive and thermal. All three types of sensors
monitor minute changes in the atmosphere in order to
calculate the humidity in the air.
• Capacitive: A capacitive humidity sensor measures
relative humidity by placing a thin strip of metal oxide
between two electrodes. The metal oxide’s electrical
capacity changes with the atmosphere’s relative
humidity. Weather, commercial and industries are the
major application areas