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A Proximity Sensor Detects An Object When The
Object Approaches Within The Detection Range And
Boundary Of The Sensor.
Proximity Sensor Includes All The Sensor That Perform
Non Contact Detection In Comparison To Sensors Such
As Limit Switch ,That Detect The Object By Physically
An Inductive proximity sensor is an electronic
proximity sensor , which detect metallic object
without touching them.
Their operating principle is based on a coil and
high frequency oscillator that creates a field in
the close surrounding of the sensing surface .
The operating distance of the sensor depends on
the coil’s size as well as the target ‘s shape, size
The Main Components Of The Inductive Proximity
Sensor Are. Coil, Oscillator, Detector And The Output
The Operating Distance Of The Sensor Depends On
The Actuator's Shape And Size And Is Strictly Linked
To The Nature Of The Material
The Coil Generates The High Frequency Magnetic
Field In Front Of The Face. When The Metallic Target
Comes In This Magnetic Field It Absorbs Some Of The
Hence the oscillator field is affected. The rise or
fall of such oscillation is identified by a threshold
circuit..that changes the output of the sensor.
they are very accurate compared to other
Have high switching rate.
Can work in harsh environmental conditions.
It can detect only metallic target.
Operating range may be limited.
Capacitive Sensor Are Used For Non Contact
Detection Of Metallic Object And Non Metallic
Object(liquid, Plastic, Wooden Material Etc.)
Capacitive Proximity Sensors Use The Variation Of
Capacitance Between The Sensor And Object Being
Capacitance Methods Are Very Sensitive ,
Distance Down To One Micro Inch Can Be Measured.
The Main Components Of The Capacitive Proximity
Sensor Are Plate, Oscillator, Threshold Detector And The
The Plate Inside The Sensor Acts As One Plate Of The
Capacitor And The Target Acts As Another Plate And The
Air Acts As The Dielectric Between The Plates.
The Capacitive Sensor Can Detect Any Targets Whose
Dielectric Constant Is More Than Air
As the object comes close to the plate of the
capacitor the capacitance increases and as the
object moves away the capacitance decreases
an electronic circuit inside the sensor begins to
oscillate. The rise or the fall of such oscillation is
identified by a threshold circuit and based on
that output switches.
It can detect both metallic and non metallic
Capacitive sensors are good in terms of power
They are affected by temperature and humidity
Difficulties in designing
Capacitive proximity sensors are not as accurate
compare to inductive sensors.
The Proximity Of The Object Is Detected By The Action
Of The Travelling Light Move.
These Sensors Use Light Sensitive Elements To Detect
Objects And Are Made Up Of An Transmitter (Light
Source) And A Receiver
The Object Within The Range Of The Sensor Can Detect
The Light Emitted By The Transmitter Focuses On The
Object Which Reflects To Be Received By The Receiver
The Reflected Waves Travel Back And Received By The
Solid State Photo Diode, Through The Receiver Lens.
They Are Useful And Can Help Many Security
They Can Easily Be Set Off And Cause Problems.
They Are Expensive Than Inductive And Capacitive
Optical proximity sensors mostly apply in
automobile/process eng. For distance
measurement, level sensing etc.
Ultrasonic Sensor Are Some Type Used In Place
Of Optical Sensors . Instead Of Using An Light
Beam , A High Frequency Sound Wave Is Used.
This Sound Wave Is Above Normal Hearing
Frequencies And Are Called Ultrasonic
Frequencies Around 40 KHz Are Common.
The Ultrasonic Sensor Can Measure Distances In
Centimeters And Inches. It Provides Good
Readings In Sensing Large-sized Objects With
The ultrasonic sensor sends out sound and receives
it back using the receiver. Together, the ultrasonic
sensor's sender and receiver look like a pair of eyes,
but it is not a sight sensor. Instead, those "eyes" are
really more like a speaker and a microphone (a sound
The Emitter And Detector Are 2 Separate Units. The
Emitter Emits The Light Which Is Detected By The
Detector. A Target Is Detected When It Passes In-between
The Emitter And Detector.
Ultrasonic proximity sensors are not affected
by atmospheric dust, snow, rain..etc
Can work in adverse conditions
Sensing distance is more compared to
inductive or capacitive proximity sensors
Ultrasonic sensors Has More Difficulties
Reading Reflections From Soft, Curved, Thin
Or Small Objects.
The global market for these proximity sensors is
expected to grow at a steady rate. Major
industries using proximity sensors are machine
tools, woodworking machines, packaging
machines and other types of machinery.
Further applications of are automatic door units
such as garage doors or doors inside buildings,
elevator doors or doors inside railway coaches.
The building and automotive sector are further
industries using high volumes of proximity