training series: level i introduction to sensors level i

Training Series: Level ITraining Series: Level I

Introduction to SensorsIntroduction to Sensors

Level I Level I

Course Topics

• Sensors Definition• Sensor Building Blocks

– Electrical Interface• Tell me about it:

– Sensing Technology• I see it:

– Housings• Looks are everything:


Level IIIAdvance Problem Solving

Level IIProducts andApplications

Level ISensorBasics


Sensor DefinitionsSensor Definitions

What are we talking about ?

What are we talking about ?

What is a Sensor?

Used in Industrial Automation:

Electrical device capable of identifying change within an automated process.

Electrical device capable of identifying change within an automated process.

Sometimes…Sensor = SwitchSometimes…Sensor = Switch


Sensor Uses• Sensors in our world

– Automatic opening doors– Grocery check-out conveyer

shut-off– Safety sensors on garage doors• Sensors in

Manufacturing– Part position verification– Counting products– Liquid level control– Quality control inspection– Personal safety systems


Sensor Building BlocksThe three major components:

The sensing sideFront-end

Housing

The electrical sideBack-end


Building Block Concept


Sensingtechnology

Electricalinterface

Housing

most any

most any

most any

The Building Blocks

Front-end - SensingFive technology choices:

• Inductive• Optical• Capacitive• Magnetic• Mechanical

Selection base on: ApplicationSelection base on: Application


The Building Blocks

Back-end – ElectricalOptions:

• Electrical voltage– AC/DC– DC

• Output type– Discrete (on-off, like a switch)– Analog

Selection base on: Control SystemSelection base on: Control System


The Building Blocks

• The Sensors Housings– Material Options:

• Metal (nickel-plated brass)• Stainless steel• Aluminum• Plastic

– Shape (mounting style):• Tubular• Block

Selection base on: EnvironmentSelection base on: Environment


The Building Blocksand the real world

Sen

sing

Housing

Electrical

App

licat

ion C

ontrol System

Environment



Electrical InterfaceElectrical Interface

The Back-endThe Back-end

Electrical Interface

Divided into 2 areas:– Operating voltage

– Output signal type


PowerPower

SignalSignal

Output Signal Types

• Discrete– ON or OFF– YES or NO

• Analog– Speed control– Position

information

MIN MAX


SignalSignal

Operating Voltage

• Direct Current (DC)– Current flows in

only ONE direction

– Safe, easy-to-handle power source

• Alternating Current (AC)– Current changes

direction 60 times a second

– Readily available


PowerPower

Basic Electrical Principals

What is electricity?

– Interesting fact: • Electron flow is similar to water flow • We will use this analogy during our class


Flow (current) or potential flow (voltage) of electrons

Flow (current) or potential flow (voltage) of electrons

Basic Series CircuitUsing Water Analogy:

Water Tank

Water Valve

Hydro motor

PotentialFlowing


Basic Series CircuitElectronics:

PotentialFlowing

+

-

BatterySwitch

Electric Motor

Basic ON or OFF operationBasic ON or OFF operation


A discrete Sensor is a Switch

Electronics

Sensing SideFront-end

Electronics

Power WiresSwitch


Electronics

Basic Sensor CircuitSensors with relay output

+

-

Unlike a switch, sensors require power to operate


Types of discrete electrical outputs

• Sensors of today use Solid-State outputs, not mechanical relays

Today Yesterday

– PNP, 3-wire Relay– NPN, 3-wire– AC/DC, 2-wire


The NPN & PNP outputFunctions similar to a switch,But current only flows in one direction

PNPTransistor Mechanical

Switch


The Different TransistorsWhat direction do you want current to flow?

NPNAlso called Sinking


PNPAlso called Sourcing

+--+

PNP, 3-wire

1

4+

PNP Output3 -

Load

Standard diagram formAs shown in our catalog

The Sensor

The LoadConnector

Pins


PNP, 3-wire

1

4+

PNP Output3 -

Load

Watching the current flow

Sensors Power

Output Signal


1

4+

NPN Output3 -

Load

NPN, 3-wireWatching the current flow

Sensors Power

Output Signal


1 ~

3 ~

Load

The 2-wire AC/DC outputFunctions similar to a switch,

But with a small leak

Sensors Power Supply from leakage current

Output Signal

Triac


Quick Reference:wiring PNP & NPN

N P NP N P

+

-

Load

First side of load

Second side of load

Switched side

Positive

Negative

Sensor is PNP


If given a choice, which discrete sensor type should I choose?

PNP or NPN, 3-wire - Fewer interface

problems- Largest selection- Lowest unit costs

AC/DC, 2-wire- Many interface issues- Smaller selection- Susceptible to noise

1st CHOICE

2nd CHOICE

1

4+

3 -

Load

1 ~

3 ~

Load


Normally Open (NO)vs.

Normally Closed (NC)Identifies the non-active state (target not present) of the sensor

Electronics

+

-

Normally Open

Is it off (open)?

Is it on (closed)?


Normally Open (NO)vs.

Normally Closed (NC)Identifies the non-active state (target not present) of the sensor

Electronics

+

-

Is it off (open)?

Is it on (closed)?

Normally Closed


Analog OutputsUnlike a discrete output with two defined states, analog signals have an infinite number of states.

Discrete

Analog

On

Off

Voltage

Time

Max

Min

Voltage

Time


Analog UsesTo provide absolute measurement or position information

MeasurementPosition


Analog Applications!What can you do with measurement information?

– Measure thickness– Position feedback– Measure tool wear– Null out machine wear– Null out thermal

expansion– Verify die position– Verify bend radius– Part profiling– Stack height

– Spool diameter– Rotational position– Liquid level– Sort parts– Determine part

orientation– Measure vibration– Measure

straightness– Hydraulic or

pneumaticcylinder position

Expanding

possibilities

Expanding

possibilities


Analog Data• We know analog information provides:

– Measurement information– Position information

• What devices use analog information?

0 10987654321

Measurement

Panel meters Control systems


Analog Information• The many forms for representing

measurement or position information

10

0

10

-10

5

-5

20

0

20

4

Voltage

Current

Digital Pulse


Analog VoltageInformation contained in varying voltage

Maximum Voltage

0 10987654321

Measurement

Half Voltage

0 10987654321

Measurement

Water Analogy Volt Meter


Analog CurrentInformation contained in varying Current

0 10987654321

Measurement

0 10987654321

Measurement

Maximum CurrentHalf Current

Water Analogy Current Meter


Digital PulseInformation contained in digital pulse timing

100.00Maximum measurementHalf wayMinimum measurement

50.000.00Pulse Width

Meter

Start/Stop


Measurement range

Measurement range

Electrical Interface REVIEW

• Operating voltage: Sensor Power– DC: Safest– AC: Most available

• Output signal types– Discrete

• PNP, 3-wire• NPN, 3-wire• AC/DC 2-wire

– Analog• Voltage• Current• Digital pulse


PowerPower

SignalSignal


Sensing TechnologiesSensing Technologies

Sensing Technologies

Non- Contact– No physical contact with target– Preferred method for sensing end products

Contact– Contact with target– Simplest method available


Contact Sensing

Mechanical switch– Contact with plunger

opens electrical contacts

Contact


Non-Contact

Popular sensing technologies– Inductive Sensors

Metal targets– Optical Sensors

Target capable of reflecting or blocking light– Capacitive Sensors

Liquids/solids– Magnetic Field Sensors

Magnets


Inductive• When voltage is applied, an electromagnetic field is

generated and extends out the face of the sensor.

• When metal enters the sensing zone, an eddy current is induced in the metal.

• The change in eddy current is detected and the sensor’s output is energized.


• Two basic Sensing types– Flush mount

• Shorter range• Sensor can be buried in metal

– Non-flush mount• Longer range• Sensor can NOT be buried in metal

Inductive


OpticalRegardless of the operating mode, all optical sensors share the same operating principle:

Light emitter• Visible red• Laser• Infrared

Light receiver

OperationEmits a light beam then

detects or measures changes in received light.


Optical

• Optical sensors offer three main sensing modes– Thru-beam

– Retroreflective

– Diffuse

Note: There are other sensing modes available, but they are covered in other courses.


Optical: Thru-Beam• Separate emitter and receiver• Beam-break operation

Target blocks beam

Emitter Receiver

Great for long range and dirty environments


Optical: Retroreflective • Emitter and receiver in one unit• Requires a reflector• Beam-break operation

Target block light beam

Reflector

Emitter

Provides good range in well defined area


• Emitter and receiver in one unit• Convenient stand-alone design• Beam-make operation

Light reflects off target

Optical: Diffuse

Simple point and shoot operation

Target


Capacitive• Detects target based on density

Simple point and shoot operation

Target

• Electrostatic field established• Target detected when field properties change


Magnetic• Detects magnetic field• Magnetic field can travel through aluminum• Used extensively with pneumatic cylinders

Magnet

NS

Sees through aluminum


Sensing TechnologiesHead-to-Head

Mechanical:

Inductive:

Optical, Thru-beam:

Optical, Retro:

Optical, Diffuse:

Capacitive:

Magnetic:

Popular, simple

Rugged, cost-

effective

Long range

Mid range

Short range

Liquid & bulk

targets

Pneumatic

cylinders



HousingsHousings

Physical looksPhysical looks

Housing Function• Protection from environment• Mounting provisions• Electrical connection

HousingsHousings

Protection from environment

– Multiple degrees of protection liquids• IP65: Protects against water mist• IP67: Protects against temporary immersion• IP68: Protects against continuous immersion

– Multiple level of physical abuse• Metal housing• Plastic housing

HousingsHousings

Mounting Provisions• Depends on shape of housing

– Tubular• Popular for short range sensors• Range adjustments made by moving sensor in

and out

– Block• Popular for optical sensors• Easy to align horizontally and vertically

HousingsHousings

Inductive SensorInductive Sensor

Tubular HousingsEasy mounting and range adjustment

Optical SensorOptical Sensor

CapacitiveCapacitive

MagneticMagnetic

HousingsHousings

Block Housings

Provides thru-holes for mounting bolts

Allows for easy beam alignment



BOS-SR2

HousingsHousings

Combination HousingsCombination of tubular and block housings



HousingsHousings

Application Specific ShapesInductive SensorInductive Sensor


MagneticMagnetic

HydraulicCylinder

RingSensor

ValvePosition Clamp

Position

SlotSensors

WindowsFiber-optics

Pneumatic Cylinders

HousingsHousings

Electrical Connection

• Cable Out version– Economical: no additional cable to

purchase– Difficult to replace sensor

• Connector version– Cost: must purchase mating cable– Much easier to replace sensor

HousingsHousings

Cable Connection Options

• Cable Lengths– Standard lengths: 2m, 3m & 5m

• Jacket Material– PVC: Standard, low cost jacketing– PuFlex: For flexing applications

HousingsHousings

Connector Options

• Industry standard connector sizes:– Micro (M12)

• Most popular, mid-size• Available in 3, 4, 5 and 8 pins

– Nano (M8)• Smallest size• Available in 3 and 4 pins

– Mini• Largest size• Available in 3 and 4 pins

HousingsHousings

Sensor HousingsREVIEW

• Protection from environment– IP65, IP67, IP68

• Mounting provisions– Tubular, Block, Combination, Application

specific shapes• Electrical connection

– Cable out and connectors

HousingsHousings

Sensor Fundamentals

Sen

sing

Housing

Electrical

App

licat

ion C

ontrol System

Environment

Sensors DefinitionsSensors Definitions

Questions & AnswersQuestions & Answers


Sensor BasicsSensor Basics

training series: level i introduction to sensors level i

Documents

type of sensor

sensor usessensors

sensor definitionswhat

sensor knowledge

application sensor definitions

sensor definitions section

sensor training introduction

sensors course