proximity sensor
DESCRIPTION
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 Contacting Them. It is a sensor able to detect the presence of nearby objects without any physical contact. A proximity sensor often emits an electromagnetic field or a beam of electromagnetic radiation (infrared, for instance), and looks for changes in the field or return signal. The object being sensed is often referred to as the proximity sensor's target. Different proximity sensor targets demand different sensors. For example, a capacitive or photoelectric sensor might be suitable for a plastic target; an inductive proximity sensor always requires a metal target. The maximum distance that this sensor can detect is defined "nominal range". Some sensors have adjustments of the nominal range or means to report a graduated detection distance. Proximity sensors can have a high reliability and long functional life because of the absence of mechanical parts and lack of physical contact between sensor and the sensed object. Proximity sensors are commonly used on smart phones to detect (and skip) accidental touch screen taps when held to the ear during a call.[1] They are also used in machine vibration monitoring to measure the variation in distance between a shaft and its support bearing. This is common in large steam turbines, compressors, and motors that use sleeve-type bearings. A change in the sensor's electric or magnetic field can also be used to determine proximity.TRANSCRIPT
Proximity sensor
SHWETA JINDALB.tech3rd year (EI)BTBTN12410Roll no. - 7733
TABLE OF CONTENTINTRODUCTIONTYPES OF PROXIMITY SENSORCONSTRUCTIONWORKINGAPPLICATIONSADVANTAGEDISADVANTAGECONCLUSIONREFRENCES
What Is A Proximity Sensor
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 Contacting Them.
INDUCTIVE PROXIMITY SENSOR
CAPACITIVE PROXIMITY SENSOR
ULTRASONIC PROXIMITY SENSOR
OPTICAL PROXIMITY SENSOR
Types of proximity sensor
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 and material
INDUCTIVE PROXIMITY SENSOR
The Main Components Of The Inductive Proximity Sensor Are. Coil, Oscillator, Detector And The Output Circuit
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 Energy
Construction and Working
Cont.. 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.
ADVANTAGES they are very accurate compared to other
technologies. Have high switching rate. Can work in harsh environmental
conditions.
DISADVANTAGES 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 Detected.
Capacitance Methods Are Very Sensitive , Distance Down To One Micro Inch Can Be Measured.
Capacitive proximity sensors
The Main Components Of The Capacitive Proximity Sensor Are Plate, Oscillator, Threshold Detector And The Output Circuit.
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
Construction and working
Cont.. 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.
ADVANTAGES It can detect both metallic and non metallic targets. Good stability High Speed Capacitive sensors are good in terms of power
usage Low cost
DISADVANTAGES 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 Presence.
OPTICAL SENSOR
The Light Emitted By The Transmitter Focuses On The Object Which Reflects To Be Received By The Receiver Photo Diode.
The Reflected Waves Travel Back And Received By The Solid State Photo Diode, Through The Receiver Lens.
ADVANTAGES They Are Useful And Can Help Many
Security Problems.
DISADVANTGES They Can Easily Be Set Off And Cause
Problems. They Are Expensive Than Inductive And
Capacitive Proximity Sensor
APPLICATION 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 Hard Surfaces.
Ultrasonic sensors
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 sensor).
Ultrasonic working
CONT.
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.
ADVANTAGES 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
DISADVANTAGES 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 sensors.
conclusion
REFRENCEShttp://literature.rockwellautomation.com/idc/groups/literature/documents/ca/c116-ca502_-en-p.pdf
http://en.wikipedia.org/wiki/Proximity_sensor
http://www.fargocontrols.com/sensors.htmlhttp://www.autonics.co.in/products/products_2.php?big=01&mid=01/01
http://www.ia.omron.com/support/guide/41/overview.html
http://www.sensorcentral.com/photoelectric/proximity01.php
http://www.engineershandbook.com/Components/proximitysensors.htm