discrete sensor and it's application

Sensor

1

Sensor Course By :

Mahmoud Taha; Demonstrator.

Benha Faculty of Engineering

Benha University

March., 2014

Sensors

Sensors can be used to:

Sensors Check position and alignmentActuators

Measure levels

Processing Recognize colors

Sort and Count targetsInstructions Reports

Measure motor speed

Human-Machine Interface

Instructor ENG / M.TAHA

2

Sensors

SensorTarget to detect Sensor output

Electric signal sent to theprocessing units:

Digital

Analog

Operating part

Target detection

Signal processing part

Data

processing

Command part

Data

transmission

3Instructor ENG / M.TAHA

Important criteria to choose a sensor :

Type of targetopacity/transparencybrilliance/reflectionshapemagnetic propertiesSpeed

Detection rangedetector-target distancecontact with the target

Detection precisionprecision in distancedetection reliability

Type of environmentcleanliness: presence of fluids, steam, dusttemperatureshocks, vibrationselectromagnetic interferenceavailable space


4

Important steps to choose a sensor :Step 1:What is the sensing distance required?

Step 2:How much space is available for mounting the sensor?

Step 3:Is a shielded or unshielded sensor needed?

Step 4:Consider environmental placement concerns and Protection Degree.

Step 5:What is the sensor output connected to?

Step 6:Do I need 2, 3, or 4-wire discrete outputs?Do I need analog outputs?

Step 7:Determine output connection type. Step 8:Switching Frequency & supply voltage


5

Inductive

Capacitive

Optical

Magnetic

Ultrasonic

mally open

rmally closed

+ 18 to 30 Volts DC.

Output

0 V Nor

No

Instructor ENG / M.TAHA6


Output configurations

+

PNP current source output(NO / NC)

GND

+

NPN current sink output)NO / NC(

GND

2wire type output (NO/ NC(

NDG

Brown

Brown

blue

black

blue

black

Brown

blue

Sensors


8


Brown

blue

black

Brown

blue

black

Sensors

with Normally open functionCapacitive Sensor

+ 18 to 30 Volts DC.

Output

0 V


Sensor connectionOutput configurations

Sensors


Sensor connection24v DC

PNP Type

Output is Positive Positive switching

+ 18 to 30 Volts DC

Output

0v

0 V


Sensors


Sensor connection24v DC

NPN Type

Output switches

through to 0v Negative switching

+ 18 to 30 Volts DC

Output

0v

0 V


Sensors


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What are sensors?

Limit switches Inductive

Photoelectric Pressure

Capacitive

RFID

Ultrasonic

Encoders


13

Detection By ContactContact-free Detection

Contact-free detection


The sensor change their output when an object is present, but not touching the sensor.

Sensors

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Principle

An inductive detector comprises an oscillator

whose coils represent the sensitive side.

The coils generate an alternative magnetic field.

When a metallic object is placed in this field,

induced currents form an additional load that

causes the oscillations to stop.

Then the detector processes the data by

generating a corresponding output signal on a

normally open (NO) or normally closed (NC)

contact.

Use

contact free detection of any metallic object

close range

even in difficult environments


15

Inductive proximity sensors


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High frequency m

Active surface

Resonant circuit coil

LED indicator

agnetic field (300 to 800 kHz)

Connection cable


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Target

Sensor

OscillationAmplitude

Sensoroutputsignal

ON

OFF


18

Target

Sensor


Sensoroutputsignal

ON

OFF


19

Target

Sensor


Sensoroutputsignal

ON

OFF


20

Target

Sensor


Sensoroutputsignal

ON

OFF


21

Target

Sensor


Sensoroutputsignal

ON

OFF


22

Target

Sensor


Sensoroutputsignal

ON

OFF


23

Target

Sensor


Sensoroutputsignal

ON

OFF


24

Target

Sensor


Sensoroutputsignal

ON

OFF


25

Target

Sensor


Sensoroutputsignal

ON

OFF


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Inductive sensorsShielding


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Proximity sensors contain coils that are wound in ferrite cores.They can be shielded or unshielded. Unshielded sensors usually have a greater sensing distance than shielded sensors.

Inductive sensors


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A correction factor can be applied when targets are smaller than the standard target.

Snew = Srated x TSnew = 1 mm x 0.83Snew = 0.83 mm

Target SizeA standard target is defined as having a flat, smooth surface, made of mild steel that is 1 mm (0.04) thick.

Inductive sensors

Formats and materials

Rectangular

Form J Form F Form E Form CC Form Form D

AccessoriesFor flat sensors forms E, C and D

Precabled orconnector

with

elbowed straight Screw-terminal


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Inductive sensors

Metal casingPlastic casing

Cylindrical

Diam 8mm Diam 18 Diam 30Diam 12mm

XSZB1** : Fixing

clamp with

indexing pin

Plastic fixingclamp

XUZB2005ShortLong

Cylindrical: Foodand BeverageIndustry

XS212SANon-Flush

XS218SANon-Flush

XS2L2SANon-Flush

XS230SANon-FlushStainless steel

fixing clamp

diam 12, 18, 30


30

Inductive sensors


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Sn = 100 %Soft steel

Sn = 45 %Brass

Sn = 35 %Aluminium

Inductive Sensors can only detect metals

Sensing distance depends on the target material used

Inductive sensors


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The target material also has an effect on the sensing distance. When the material is other than mild steel correction factorsneed to be applied.

Target Material

Inductive sensors


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Application

Detecting Presence of Set Screws on Hub for Speed or Direction Control

Detecting Broken Bit on Milling Machine

Advantages Disadvantages Applications

Resistant to Harsh Environments

Very Predictable Long Life Easy to Install

Distance Limitations Limited to metal

Industrial and MachinesMachine Tool Senses Metal- Only

Targets

Inductive sensors


34

capacitive sensors

PrincipleA capacitive detector is primarily made up of anoscillator whose capacitors form the sensitive

sides.Whena conductive or insulatingmaterial with a permittivity level >1 is placed in this field, it changes

the coupling capacitance and triggers oscillations.Then the detector processes the data by

generating a corresponding output signal on a normally open(NO) or normally closed (NC) contact.

Use contact free detectionof all kinds of objects whether metallic or not, as well as liquids and sprays, close range.


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capacitive sensors


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How they work


37

Electrostatic fieldSensor is looking for a change incapacitance in the active field

Active surface

LED indicator

Active electrode

Earth electrode

Adjusting screw

Connection cable


38

Target


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40


41


42

capacitive sensors


43

For this sensor the proximity of any material

near the electrodes will increase the

capacitance. This will vary the material of the

oscillating signal and the detector will decide

when this is great enough to determine

proximity.

The object is a dielectric material of capacitor.

Dielectric type

There are 2 types of capacitive sensors

Dielectric type

Conductive type

capacitive sensors


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For this sensor the proximity of conductive

material only near the electrodes will

increase the capacitance. This will vary the

material of the oscillating signal and the

detector will decide when this is great

enough to determine proximity.

The object is the 2nd plate of capacitor.

Conductive type


Schneider Capacitive sensors: a sample

Diam12

Diam18

Diam30

Multi-currentMulti-voltage

XT740X40


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46

Sensor is adjusted so that it

does not see the wall of vessel


47

As the level risesaffects the sensor

the fluid field.


48

Until the sensor switches.


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capacitive sensors


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Application

Controlling Fill level of solids in a bin

Detecting Milk in Cartons


Detects Through Some Containers

Can Detect Non-Metallic Targets

Very Sensitive to Extreme Environmental Changes

Level Sensing

capacitive sensors


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Proximity sensor application

Photoelectric sensorsOptoelectronic components

Emitting component

The photoelectric sensors use light emitting diodes (LED) which transform the electric signal into

a monochromatic luminous signal.

iW.L: 660 nm

Receiving component

Electric current is generated in the photodiode or phototransistor by photoluminescence effect.

A specific component is used for Osiconcept: OPIC (Optical Integrated Circuit)

i

Red emissionInfrared emissionW.L : 890 nm


55

Principle

Photoelectric sensors combine a light source,

generally an infrared light source and a light

receiver. Detection happens when light beam is

broken. Detection happens without any contact

with the target.

reflector

Use

any opaque object, regardless of shape and material

reflective and transparent tagets require polarized

reflex technology

the presence of a background behind the target is

to be taken into account a clean environment is required

long distance detection is possible in

through-beam mode


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Photoelectric Sensors


Photoelectric sensors: a sample

LASER Cells


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Sensors

Photoelectric sensors

Detection operating modes

Photoelectric sensors: Operating modes

Through-beam:long

distance detection

Diffuse: using target reflective properties

Polarized reflex: For detecting

shiny/transparent objects.

Reflex: for opaquetargets


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59

Transmitter Receiver


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61

Target



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63



64



65



66



67



68



69

Target



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Through-beam mode

merits:

used for long distances

precise and reliable detection,

adapted to rough environments,

detection of shiny objects,

no dead zone.

Demerits:

2 cases to be wired (separate transmitter and receiver)

Infrared technology Difficult adjustment forlong distance.

Note:

The diameter of the light beam is known and determines the minimum size of an object that can be detected.


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Transmitter /Receiver

Reflector(prismatic)

T

R


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Reflector (prismatic)

T

R


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T

R


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Optical sensors (Retro-reflective)

Type : Retro reflective Target



T

R


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T

R


78



T

R


79



T

R


80



T

R


81



T

R


82



T

R


83



T

R


84


85

Reflex mode

merits:

short or average sensing distance,

single case (transmitter + receiver),

easy installation.

Demerits:

sensitive to shiny objects,

dead zone depends on type of reflector.

Note:

generally, the object to be detected must bebigger than the reflector,

avoid the interference reflections (shiny objects or background).


86



Polarized Reflex mode

merits:

single case (transmitter + receiver),

short or average sensing distance,

detection of reflective objects,

easy installation.

Polarizingfilters Reflector

depolarizeslight

Demerits:

Shorter range than standard reflex

Note:Shiny target does not

depolarize light and is detected by the

sensor

generally, the object to be detected mustbe bigger than the reflector,

some plastic materials (film, packaging...) depolarize the light.


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Optical sensors (Diffuse)

Type : Diffuse


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Type : Diffuse Target

Transmitter /ReceiverT

R


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Type : Diffuse


R


90


Type : Diffuse


R


91


Type : Diffuse


R


92


Type : Diffuse


R


93


Type : Diffuse


R


94


Type : Diffuse


R


95


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Diffuse system

merits:

one single case (emitter + receiver),

detection of target with high reflection coefficient (from 0.6 to 0.9 )

Demerits:

short sensing distances,

sensitive to the reflection factor of the object(surface state and colour)

dead zone,

sensitive to the background.

Note:

fixed or adjustable sensitivity.


97




Photoelectric sensors: Why use laser technology?

Laser sensors are used where detection of smallobjects or precise positioning is required

Laser light consists of light waves of a singlewavelength, high in energyand power density

because the waves are in phase with each other

Tightly focused, almost parallel light beam that candetect very small objects at long ranges

Laser light: wave representation

The light beam is visible, and during set-up of thesensor, the laser power is increased. This provides a

bright light spot clearly visible even in the daylight, which aids alignment

Detecting holes on aprinted circuit board

Checking the shapeof a dental mold


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Sensors



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Verifying Objects in Clear Bottles

Counting Cans

Detecting Persons

Controlling Parking Gate



100

Determining Orientation of IC Chip

Counting Boxes Anywhere on a Conveyor

Detecting Components Inside Metal Can

Detecting Caps on Bottles



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Senses all Kinds of Materials

Long Life Longest Sensing

RangeVery Fast Response

Time

Lens Subject to Contamination

Sensing Range Affected by Color and Reflectivity of Target

PackagingMaterial HandlingParts Detection

Sheet Printing application

Reflected wavePrincipleUltrasonic sensors have an acoustic transducer which is vibrating at ultrasonicfrequencies.

Emitted wave

The pulses are emitted in a cone-shapedbeamand aimedat a target object. Pulses reflected by the target to the

sensor are detected as echoes.

The device measures thetime delay betweeneachemitted and echo pulse to accurately determine the sensor-

to-targetdistance.

UseNon-contact detectionof many materials regardless of target color, transparency, shape, in environments where other

sensingtechnologieshave difficulty, suchas clear or shiny objects, foggyor particle-ladenair or splashing liquids.


104

Ultrasonic sensors

Ultrasonic sensors

Sensing window

DeadbandSensing Window

two limits are

adjustable according to

Far Limit

(In our offer, the

fixed orthe product)

Near Limit

Range


105


106

Ultrasonic sensors

Ultrasonic sensors

Example of application


107

Ultrasonic sensors


The ApplicationConveyor line that is two feet wide with two belts running

glass jars and plastic bottles providing an accumulationahead of a labeling machine.


108

Ultrasonic sensors


Application:

Robotic arm positioningRobotics are used throughout the glassmanufacturing industry to pick up glass plates andreposition them for different processes.

In this application, a robotic arm is used to place asheet of glass on a conveyor belt.

This application is difficult because theenvironment is dirty or wet and the material is

transparent

Analog sensor to measure a distance


109

Ultrasonic sensors


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Level Measurement in Large Vessels (Tanks)

Level Measurement in Small Bottles

Quality Control

Anti-Collision


Ultrasonic sensors


111

People Sensing

Diameter Sensing and Strip Speed Control

Bottle Counting



Senses all Materials

Resolution Repeatability Sensitive to

Temperature Changes

Anti-Collision Doors Level Control

Ultrasonic sensors



113

Sensor Objects Detected Technology

Inductive Metal Electromagnetic Field

Capacitive Any Electrostatic Field

Ultrasonic Any Sound Waves

Photoelectric Any Light


Detection by contact


114

The sensor change its output when an object is physically touching the switch.

Sensors

"F"

Limit switches

Introduction

An interface between mechanicalposition and electrical control function.

An electromechanical detection deviceadapted for industrial environments.

Converts a mechanical action into anelectrical signal.

"O" "O"

"F"Electrical signal into the

control circuit of a machine


115

Principle

The target acts on a mechanical contact via a

command lever. Depending on the position of

the lever, the contact will be actuated or not.

Use and limits

For detection by contact Used on targets that will not deform, regardless of shape, type, composition or colour.

For precision detection applications, it is possible to combine a detector with cams.


116

Limit switches

Limit switches

Control devices

Direction

Operating speed

Positivity

Risk of damage in case of Very high

overrun

Target type

TYPE OF PLUNGER

Simple plunger Roller plunger Ball plunger

0,5m/s

Yes

0,6-1m/s

Yes

High

30

0,1m/s

Yes

High

30


117

Limit switches

Control devices

Direction

Operating speed

Positivity

Risk of damage

Type of target

Operated contact Non-operated contact

LEVERAND ROLLER LEVER PLUNGER STYLE

Or

1m/s

Yes

Medium

30

1-1,5m/s

Yes No

Medium High

30


118

Limit switches

Control devices

Direction

Operating speed

Positivity

Risk of damage

Type of target

Operated contact Non-operated contact

ROTARYSTYLE

M P

Spring return to center Positionmaintained

OR OR

Non-programmable Programmable

1-1,5m/s

Yes (only with rigid levers)

Low

Actuation Release

0,5

Low


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Limit switches

Control devices

Direction

Operating speed 0,5 - 1m/s

Positivity No

Risks of damages Lowest

Type of target

MULTI-DIRECTIONALHEADS

8


120

Limit switches

Plunger style head

End plunger style Roller plunger style


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Limit switches

Rotary style head


122

Limit switches

Multi-direction head


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Limit switches


124


High Current Capability Low Cost Familiar "Low-Tech"

Sensing

Requires Physical Contact with Target

Very Slow Response Contact Bounce

Basic End-of- Travel Sensing

Detectionby contact

Schneider Limit switches: a sample


125

Sensors

Rotary Encoders

An encoder is an angular position sensor:

connected mechanically to a shaft that drives it, with its shaft turning a disk attached to it. The disk comprises a successionof opaque and transparent parts.

uses the light emitted by Light Emitting Diodes (infrared LEDs), which passes through the notches in the disk so that an analogue signal is created for the receiver photodiodes. this signal is electronically amplified and then converted into a square wave signal which is then sent to a processing system.

An encoder is therefore made up of three parts:

ELECTRONIC

readings and output

signals

MECHANICALencoder shaft

OPTICALgraduated disk

Flex. coupling Shaft

Reticle

LED


126

To countingelectronicsPrinciple

The shaft of an encoder is coupled with

the shaft of the spinning system to be

monitored. An ingenious photoelectric and

processing system converts shaft

revolutions into electrical signals which

can be processed by counters,

tachometers, PLCs, etc.

Transmitter

Receiver

Shaft

Use

Detection of angle, position, speed,

acceleration and linear motion.


127

Rotary Encoders

Photo sensor

diode

Photo sensor

diode

Rotating disk blockinglight

Photo sensor has a lowlogic output

Rotating disk allowing light through

Photo sensor has ahigh logic output

Continuous train of pulses formed as the photo sensor traverses between logic high and logic low in response to the rotation of the disk

Logical 0 Logical 1

Rotary Encoders


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Principle of operation

Rotary EncodersIncremental Encoders

Type of output signal:

Pulse train sent

Period or increment(1) Electrical degree

Pulse up/down counting by the processing unit makes it possible to determine the position of themoving part.

The signal processing (e.g. the PLC), totalises

the +1 or -1 counts, depending on the direction

of rotation:

Forward-Up counting:

Counter value +1

Reverse-Down counting:

Counter value -1


129

Rotary EncodersAbsolute Encoders

These encoders are called absolute encoders for they provide anabsolute position as soon as the machine is powered up.

-Most often, they use an optical disk with Gray code or binary tracks. Gray code is designed to allow only oncechange of code for each successive state. As only one digit changes state (1 or 0), this avoids any uncertainty in

the successionof codes.-In the same way as when using an incremental encoder, the light intensity varies for the tracks hide the light source and generate analogue signals that are converted into square wave signals for each of the tracks.

-One signal per track is available: either 1 or 0, called a "bit". The successionof 1s and 0s forms the code thatcorresponds to a single position. The encoder provides the absolute position of the complete disk/axis assembly

and consequently of the mechanism coupled to it and whose position is to be measured (motor shaft, robot arm,etc.). There is no need to reset the point of origin every time the machine is powered up.

-The number of bits determines the resolution. The LSBs correspond to the highest precision level while the MSBscorrespond to the lowest position.


130

courtesy Parker

Motion & Control

Absolute digital position: Gray encoder

1 2 3 4 5 6 7 8 9 10 11 12 13 140 15

1 2 3 4 5 6 7 8 9 10 11 12 13 140 15

LSB

MSB

LSB

MSB

binary code: if all bits were to change at about the same time: glitches

Gray code: only one bit changes at a time: no glitch

Gray disk (8 bit)

0000

0001

0010

0011

0100

0101

0110

0111

0000

0001

0011

0010

01100111

0101

0100


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Absolute Optical Encoder

In the fig word size of data is 4bits. Outermost Element is LSB. Innermost Element is MSB. The Angular position is given as=360/24.

The direct binary representation of the disk sector shown in the table


132

Rotary Optical Absolute Encoder


133

Rotary EncodersAbsolute Encoders vs Incremental Encoders

Incremental encoders Absolute encoders

power break

power breaks

signals

configuration over the bus

Advantages DrawbacksAdvantages Drawbacks

- Low Price-Only generates pulses relative

position .

-Requires an end of travel

stop for resetting the

processing system called

"recalibration"

-Requires a little program in

the PLC to generate the

signal

-Pre-processing may

require recalibration after a

power break

-Sensitivity to line

interference

-Cannot reset using a zero

point when an oscillating type motion is used that never

achieves a complete revolution.

-Provides a value for the

absolute position

-No loss of position after a

--> Insensitive to mains

--> Insensitive to spurious

-Can withstand complete

and troubleshooting.

-High price


134

Rotary EncodersTrends and various information

Why several encoder diameters?

The encoder size is directly linked to the size of the ball-bearings used for shaft rotation.

Hence the greater the diameter, the better its resistance to impact, vibration, misalignment and otherconstraints (radial loads).

- 40mm micro-robotics (lowmechanical loads and vibration), small motors.

- 58mmuniversal encoders, suitable for all types of applications (packaging, cutting, cross tabletransfer, textiles, robotics, automatic tool storage)

- 90mm heavy and harsh industry environments: steelmaking, glass, paper, food and beverageindustries, automakers, heavy hoisting.

Note: In our product range, solid-shaft encoders always have a longerservice life than through-shaft encoders.

This is due to the ball-bearing shape: extra flat for through shaft encoders against standard ones for the solidshaft range.

The most universal product is the 58mm, 5-30VDC supply, RS422 output unit.


135

Principle: Electronic PressureSensors Principle: ElectromechanicalPressureSensors

Pressure is applied to bellowS. When it

reaches the level set by the user using spring R, microswitchM changes to position1.Where pressure regulation is used, the setting

of spring R determines the switching gap on the microswitchwhen pressure falls.

Detection is based on a ceramic pressuremeasuring cell. The deformationcaused by

pressure is interpreted as a change in resistance. The change is then processedby integrated electronics yielding a digital or

analog output signal.

connector

CMS electronics

Ceramic cell

Note: Depending on the pressure level and the type of fluid, bellowsmay be

replaced by a membrane or a piston.


136

Pressure sensors

Sensors in the automotive industry

Weld-resistant sensor

XS1MPAW01D

Weld-resistant sensorXS1MPAW01D

Universal inductivesensor

Flat inductivesensor

PressureSwitch

Limit switch

Universal inductivesensor Safety Limit switch

with spindle

137

Sensor Application


Sensors in the material handling industry

Interlockingsafety switch

PressureSwitch

Splitter boxLasersensor

Key

safety

switchCoded

magnetic

switch

Apmlifier for fiberoptics

Trip wireE-stop

Markreader

Through- beam

Photoelecric

sensorCapacitive

proximity

sensorMiniaturephotocell

Compactlimit switch

138

Sensor Application


Sensor Application Sensors in the food industry

Pressureswitch

Ultrasonicsensor

Limit switchColor sensor withfiber optics

NEMA Limitswitch

Increased range

Inductive

proximity sensor

Safety LightCurtains

Compact limitswitchIncreased range

Inductive

proximity sensorStainless Steel

Inductive

proximity sensor Incrementalencoder

Splitter box


AnimBottling application

Sensor Data sheet


discrete sensor and it's application

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