Sensors - Atuators
Sensors - Atuators
Sensors - Atuators
Hall-Effect Position
Sensor That Shields
the Magnetic
Circuit
Optical Crankshaft Position Sensor
• In a sufficiently clean environment a shaft position can also be
sensed using optical techniques.
• Again, as with the magnetic system, a disk is directly coupled
to the crankshaft.
• This time, the disk has holes in it that correspond to the
number of tabs on the disks of the magnetic systems.
• Mounted on each side of the disk are fiber-optic light pipes.
• The hole in the disk allows transmission of light through the
light pipes from the light-emitting diode (LED) source to the
phototransistor used as a light sensor.
• Light would not be transmitted from source to sensor when
there is no hole because the solid disk blocks the light.
• The pulse of light is detected by the phototransistor and
coupled to an amplifier to obtain a satisfactory signal level.
• The output pulse level can very easily be standard transistor
logic levels of + 2.4 V for the high level and + 0.8 V for the low
level.
• One of the problems with optical sensors is that they must be
protected from dirt and oil; otherwise, they will not work
properly.
• They have the advantages that they can sense position
without the engine running and that the pulse amplitude is
constant with variation in speed.
MAP Sensor Concepts
• It is interesting to note that none of the MAP sensors in use
measures manifold pressure directly, but instead measure the
displacement of a diaphragm that is deflected by manifold
pressure.
• The primary sensor for fuel control is the exhaust gas oxygen
sensor.
Exhaust Gas Oxygen Sensor
• The amount of oxygen in the exhaust gas is used as an indirect
measurement of the air/fuel ratio.
• As a result, one of the most significant automotive sensors in
use today is the exhaust gas oxygen (EGO) sensor.
• This sensor is often called a lambda (λ) sensor