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Training Series: Level I
Introduction to Sensors
Level I
Training Series: 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 I
Sensor
Basics
Level II
Products and
Applications
Level III
Advance Problem Solving
Training Series: Level I
Sensor Definitions
What are we talking about ?
Sensor Definitions
What is a Sensor?
Used in Industrial Automation:
Electrical device capable of identifying
change within an automated process.
Sometimes…
Sensor = Switch
Sensor Definitions
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
Sensor Building Blocks
The three major components:
The sensing side
Front-end
The electrical side
Back-end
Housing
Sensor Definitions
Building Block Concept
most any
Sensing
technology
most any
Housing
most any
Electrical
interface
Sensor Definitions
The Building Blocks
Front-end - Sensing
Five technology choices:
•
•
•
•
•
Inductive
Optical
Capacitive
Magnetic
Mechanical
Selection base on: Application
Sensor Definitions
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
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
The Building Blocks
and the real world
Housing
Environment
Training Series: Level I
Electrical Interface
The Back-end
Electrical Interface
Electrical Interface
Divided into 2 areas:
– Operating voltage
Power
– Output signal type
Signal
Electrical Interface
Output Signal Types
• Discrete
– ON or OFF
– YES or NO
• Analog
– Speed control
– Position information
MIN
MAX
Signal
Electrical Interface
Operating Voltage
• Direct Current (DC) • Alternating Current (AC)
– Current flows in only
ONE direction
– Safe, easy-to-handle
power source
– Current changes direction
60 times a second
– Readily available
Power
Electrical Interface
Basic Electrical Principals
What is electricity?
Flow (current) or potential flow
(voltage) of electrons
– Interesting fact:
• Electron flow is similar to water flow
• We will use this analogy during our class
Electrical Interface
Basic Series Circuit
Using Water Analogy:
Potential
Flowing
Water Valve
Hydro motor
Water Tank
Electrical Interface
Basic Series Circuit
Electronics:
Potential
Flowing
Battery
Switch
+
Electric Motor
Basic ON or OFF operation
Electrical Interface
A discrete
Sensor is a Switch
Electronics
Sensing Side
Electronics
Power Wires
Front-end
Switch
Electrical Interface
Basic Sensor Circuit
Sensors with relay output
Electronics
Unlike a switch,
sensors require
power to operate
+
-
Electrical Interface
Types of discrete
electrical outputs
• Sensors of today use Solid-State
outputs, not mechanical relays
Today
Yesterday
– PNP, 3-wire
– NPN, 3-wire
– AC/DC, 2-wire
Relay
Electrical Interface
The NPN & PNP output
Functions similar to a switch,
But current only flows in one direction
PNP
Transistor
Mechanical
Switch
Electrical Interface
The Different Transistors
What direction do you want current to flow?
NPN
PNP
Also called Sinking
Also called Sourcing
+
-
-
+
Electrical Interface
PNP, 3-wire
Standard diagram form
As shown in our catalog
The Sensor
1
4
+
PNP Output
Load
3
Connector
Pins
The Load
Electrical Interface
PNP, 3-wire
Watching the current flow
Sensors Power
Output Signal
1
4
3
+
Load
PNP Output
-
Electrical Interface
NPN, 3-wire
Watching the current flow
Sensors Power
Output Signal
1
4
3
+
Load
NPN Output
-
Electrical Interface
The 2-wire AC/DC output
Functions similar to a switch,
But with a small leak
Sensors Power
Triac
Supply from leakage current
Output Signal
1
3
Load
~
~
Electrical Interface
Quick Reference:
wiring PNP & NPN
NPN
PNP
Sensor is PNP
+
Positive
-
Negative
Load
Electrical Interface
If given a choice, which discrete sensor
type should I choose?
1st CHOICE
1
4
+
Load
3
-
2nd CHOICE
1
3
Load
~
~
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
Electrical Interface
Normally Open (NO)
vs.
Normally Closed (NC)
Identifies the non-active state (target not present)
of the sensor
Is it off (open)?
Is it on (closed)?
Normally Open
Electronics
+
-
Electrical Interface
Normally Open (NO)
vs.
Normally Closed (NC)
Identifies the non-active state (target not present)
of the sensor
Is it off (open)?
Is it on (closed)?
Normally Closed
Electronics
+
-
Electrical Interface
Analog Outputs
Unlike a discrete output with two defined states,
analog signals have an infinite number of states.
Discrete
Voltage
On
Off
Analog
Time
Voltage
Max
Min
Time
Electrical Interface
Analog Uses
To provide absolute measurement or
position information
Measurement
Position
Electrical Interface
Analog Applications!
What can you do with measurement information?
– Measure thickness
– Spool diameter
– Rotational position
– Position feedback
– Liquid level
– Measure tool wear
– Sort parts
– Null out machine wear
– Determine part
– Null out thermal
orientation
expansion
– Measure vibration
– Verify die position
– Measure straightness
– Verify bend radius
– Hydraulic or pneumatic
– Part profiling
cylinder position
– Stack height
Expanding
possibilities
Electrical Interface
Analog Data
• We know analog information provides:
– Measurement information
– Position information
• What devices use analog information?
Panel meters
2 3 4 5 6 7 8 9
0 1
10
Measurement
Control systems
Electrical Interface
Analog Information
• The many forms for representing
measurement or position information
10
10
5
0
20
-10
20
-5
0
4
Voltage
Current
Digital Pulse
Electrical Interface
Analog Voltage
Information contained in varying voltage
Maximum
Half Voltage
Voltage
2 3 4 5 6 7 8 9
0 1
10
Measurement
Water Analogy
Volt Meter
Electrical Interface
Analog Current
Information contained in varying Current
Maximum
Half Current
Current
2 3 4 5 6 7 8 9
0 1
10
Measurement
Water Analogy
Current Meter
Electrical Interface
Digital Pulse
Information contained in digital pulse timing
Measurement
range
Maximum
Minimum
Half
measurement
measurement
way
Pulse Width
150.00
00.00
0.00
Meter
Measurement
range
Start/Stop
Electrical Interface
Electrical Interface
REVIEW
• Operating voltage: Sensor Power
Power
– DC: Safest
– AC: Most available
• Output signal types
Signal
– Discrete
• PNP, 3-wire
• NPN, 3-wire
• AC/DC 2-wire
– Analog
• Voltage
• Current
• Digital pulse
Training Series: Level I
Sensing Technologies
Sensing Technologies
Sensing Technologies
Non- Contact
– No physical contact
with target
– Preferred method for
sensing end
products
Contact
– Contact with target
– Simplest method
available
Sensing Technologies
Contact Sensing
Mechanical switch
– Contact with plunger
opens electrical
contacts
Sensing Technologies
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
Sensing Technologies
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.
Sensing Technologies
Inductive
• 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
Sensing Technologies
Optical
Regardless of the operating mode, all optical
sensors share the same operating principle:
Operation
Emits a light beam then
detects or measures changes
in received light.
Light emitter
• Visible red
• Laser
• Infrared
Light receiver
Sensing Technologies
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.
Sensing Technologies
Optical: Thru-Beam
• Separate emitter and receiver
• Beam-break operation
Target blocks beam
Emitter
Receiver
Great for long range and dirty environments
Sensing Technologies
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
Sensing Technologies
Optical: Diffuse
• Emitter and receiver in one unit
• Convenient stand-alone design
• Beam-make operation
Light reflects off target
Target
Simple point and shoot operation
Sensing Technologies
Capacitive
• Detects target based on density
• Electrostatic field established
• Target detected when field properties change
Target
Simple point and shoot operation
Sensing Technologies
Magnetic
• Detects magnetic field
• Magnetic field can travel through aluminum
• Used extensively with pneumatic cylinders
Magnet
S N
Sees through aluminum
Sensing Technologies
Sensing Technologies
Head-to-Head
Mechanical: Popular, simple
Inductive: Rugged, cost-effective
Optical, Thru-beam: Long range
Optical, Retro: Mid range
Optical, Diffuse: Short range
Capacitive: Liquid & bulk targets
Magnetic: Pneumatic cylinders
Training Series: Level I
Housings
Physical looks
Housings
Housing Function
• Protection from environment
• Mounting provisions
• Electrical connection
Housings
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
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
Housings
Tubular Housings
Easy mounting and range adjustment
Inductive Sensor
Capacitive
Optical Sensor
Magnetic
Housings
Block Housings
Provides
Inductive Sensor
thru-holes
for mounting
bolts
Allows for
easy beam
alignment
Optical Sensor
BOS-SR2
Housings
Combination Housings
Combination Inductive Sensor
of tubular and
block
housings
Optical Sensor
Housings
Application Specific
Shapes
Inductive Sensor
Hydraulic
Cylinder
Ring
Sensor
Magnetic
Valve
Position
Clamp
Position
Optical Sensor
Slot
Sensors
Pneumatic
Cylinders
Windows
Fiber-optics
Housings
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
Cable Connection Options
• Cable Lengths
– Standard lengths: 2m, 3m & 5m
• Jacket Material
– PVC: Standard, low cost jacketing
– PuFlex: For flexing applications
Housings
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
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
Sensor Fundamentals
Questions & Answers
Housing
Environment
Training Series: Level I
Sensor Basics