SensorBasics Level I

7/31/2019 SensorBasics Level I

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Training Series: Level I

Introduction to Sensors


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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


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Sensor Definitions


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What is a Sensor?

Used in Industrial Automation:

Electrical device capable of identifyingchangewithin an automated process.

Sometimes

Sensor = Switch

Sensor Definitions


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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 Definitions


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Sensor Building Blocks

The three major components:

The sensing sideFront-end

Housing

The electrical sideBack-end

Sensor Definitions


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Building Block Concept

Sensor Definitions

Sensingtechnology

Electricalinterface

Housing

most any

most any

most any


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The Building Blocks

Front-end - Sensing

Five technology choices:

Inductive

Optical

Capacitive

Magnetic

Mechanical

Selection base on: Application

Sensor Definitions


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The Building Blocks

Back-end Electrical

Options:

Electrical voltage AC/DC

DC

Output type

Discrete (on-off, like a switch) Analog

Selection base on: Control System

Sensor Definitions


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The Building Blocks

The Sensors Housings

Material Options:

Metal (nickel-plated brass) Stainless steel

Aluminum

Plastic

Shape (mounting style):

Tubular

Block

Selection base on: Environment

Sensor Definitions


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The Building Blocks

and the real world

Housing

Environment

Sensor Definitions


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Divided into 2 areas:

Operating voltage

Output signal type


Power

Signal


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Output Signal Types

Discrete

ON or OFF

YES or NO

Analog

Speed control

Position information

MIN MAX


Signal


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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


Power


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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


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Basic Series Circuit

Using Water Analogy:

Water Tank

Water Valve

Hydro motor

PotentialFlowing



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Basic Series Circuit

Electronics:

PotentialFlowing

+

-

BatterySwitch

Electric Motor

Basic ON or OFF operation



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A discrete

Sensor is a Switch

Electronics

Sensing Side

Front-end

Electronics

Power WiresSwitch



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Electronics

Basic Sensor Circuit

Sensors with relay output

+

-

Unlike a switch,sensors requirepower to operate



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Types ofdiscrete

electrical outputs

Sensors of today use Solid-State

outputs, not mechanical relaysToday Yesterday

PNP, 3-wire Relay

NPN, 3-wire

AC/DC, 2-wire



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The NPN & PNP outputFunctions similar to a switch,

But current only flows in one direction

PNP

Transistor MechanicalSwitch



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The Different Transistors

What direction do you want current to flow?

NPNAlso called Sinking


PNPAlso called Sourcing

+--+


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PNP, 3-wire

1

4

+

PNP Output

3 -

Load

Standard diagram formAs shown in our catalog

The Sensor

The LoadConnector

Pins



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PNP, 3-wire

1

4

+

PNP Output

3 -

Load

Watching the current flow

Sensors Power

Output Signal



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1

4

+

NPN Output

3 -

Load

NPN, 3-wire

Watching the current flow

Sensors Power

Output Signal



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1 ~

3 ~

Load

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

But with a small leak

Sensors PowerSupply from leakage current

Output SignalTriac



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Quick Reference:

wiring PNP & NPN

N P NP N P

+

-

Load

Positive

Negative

Sensor is PNP



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If given a choice, which discretesensortype 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



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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)?



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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



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

Discrete

Analog

On

Off

Voltage

Time

Max

Min

Voltage

Time



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Analog UsesTo provide absolute measurement orposition information

MeasurementPosition



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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



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Analog Information

The many forms for representingmeasurement or position information

10

0

10

-10

5

-5

20

0

20

4

Voltage

Current

Digital Pulse



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Analog Voltage

Information contained in varying voltage

Maximum Voltage

0 1098

7654321

Measurement

Half Voltage

0 1098

7654321

Measurement

Water Analogy Volt Meter



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Analog Current

Information contained in varying Current

0 1098

7654321

Measurement

0 1098

7654321

Measurement

Maximum CurrentHalf Current

Water Analogy Current Meter



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Digital Pulse

Information contained in digital pulse timing

100.00Maximum measurementHalf wayMinimum measurement

50.000.00Pulse WidthMeter

Start/Stop


Measurementrange

Measurementrange


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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


Power

Signal



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Sensing Technologies

S i T h l i


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Non- Contact

No physical contactwith target

Preferred method forsensing endproducts

Contact

Contact with target

Simplest methodavailable


S i T h l i


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Contact Sensing

Mechanical switch

Contact with plunger

opens electricalcontacts


S i T h l i


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Non-Contact

Popular sensing technologies Inductive Sensors

Metal targets

Optical SensorsTarget capable of reflecting or blocking light

Capacitive Sensors

Liquids/solids Magnetic Field Sensors

Magnets




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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 eddycurrent is induced in the metal.

The change in eddy current is detected and thesensors output is energized.




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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




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OpticalRegardless of the operating mode, all opticalsensors share the same operating principle:

Light emitter Visible red Laser Infrared

Light receiver

OperationEmits a light beam thendetects or measures changes

in received light.




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Optical

Optical sensors offer three mainsensing modes

Thru-beam

Retroreflective

Diffuse

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




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Optical: Thru-Beam Separate emitter and receiver

Beam-break operationTarget blocks beam

Emitter Receiver

Great for long range and dirty environments




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

Target block light beam

ReflectorEmitter

Provides good range in well defined area




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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




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Capacitive Detects target based on density

Simple point and shoot operation

Target

Electrostatic field established

Target detected when field properties change




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Magnetic Detects magnetic field Magnetic field can travel through aluminum

Used extensively with pneumatic cylinders

Magnet

N

S

Sees through aluminum




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Head-to-HeadMechanical:

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




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Housings

Housings


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Housing Function

Protection from environment

Mounting provisions

Electrical connection

Housings

Housings


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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

Housings

Housings


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Mounting Provisions

Depends on shape of housing

Tubular

Popular for short range sensors

Range adjustments made by moving sensor inand out

Block

Popular for optical sensors

Easy to align horizontally and vertically

g

Housings


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Inductive Sensor

Tubular HousingsEasy mounting and range adjustment

Optical Sensor

Capacitive

Magnetic

g

Housings


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Block Housings

Providesthru-holesfor mountingbolts

Allows foreasy beamalignment

Inductive Sensor

Optical Sensor

BOS-SR2

g

Housings


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Combination HousingsCombinationof tubular andblockhousings

Inductive Sensor

Optical Sensor

g

Housings


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Application Specific

ShapesInductive Sensor

Optical Sensor

Magnetic

HydraulicCylinder

RingSensor

ValvePosition Clamp

Position

SlotSensors

WindowsFiber-optics

PneumaticCylinders

g

Housings


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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

Housings


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Cable Connection Options

Cable Lengths

Standard lengths: 2m, 3m & 5m

Jacket Material PVC: Standard, low cost jacketing

PuFlex: For flexing applications

Housings


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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

Housings


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Sensor Housings

REVIEW Protection from environment

IP65, IP67, IP68

Mounting provisions Tubular, Block, Combination, Application

specific shapes

Electrical connection Cable out and connectors

Sensors Definitions


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Sensor Fundamentals

Housing

Environment

Questions & Answers



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Sensor Basics

SensorBasics Level I

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