2023 chapter 2 1 1 3 final

Proximity sensors ON-OFF sensors• A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact... Types of Proximity Sensors• Inductive Proxi

SENSORSAND ACTUATORS

Dr Toan Tran-HuuEmail: tranhuutoan@iuh.edu.vn

E-Learning: Trần Hữu Toàn

ocw.fet.iuh.edu.vn

© Dr H T Tran - IUH

CHAPTER II SENSORS &

CONVERTERS

2

© Dr H T Tran - IUH

2.1 Proximity sensors (ON-OFF sensors)

• A proximity sensor is a sensor able to detect the presence

of nearby objects without any physical contact

• Output signal of a proximity sensor is commonly digital

(ON/OFF)

D bé (mm)

Types of Proximity Sensors

• Inductive Proximity Sensors

• Capacitive Proximity Sensors

• Optical Proximity Sensors

• Ultrasonic Proximity Sensors

• Laser Proximity Sensors

2.1.1 Inductive Proximity Sensors

Inductive Proximity Sensors

2.1.1 Inductive Proximity Sensors

inductance is most often associated with coils

L = 

I webber ampere or [henry]

Operating Principles

a Principle

Operating Principles

a Principle

Eddy current principle

power than it would otherwise supply and hence, given a constant current, its effective resistance increases.

terms or as a change in the phase of the measured voltage (given a constant current).

media.

a Principle

b Construction

c Symbol

GND

Vcc

Output signal

Will detect any conductive material

Quoted distances are for mild steel

Sensor performance can be affected by:

• Temperature

• Target material

• Target dimensions

d Properties

Operating Distance Correction Factors

Flat targets are preferable

Targets larger than the sensing face may increase the

sensing distance

d Properties

Targe t

d Properties

TargetSensor

TargetSensor

TargetSensor

TargetSensor

TargetSensor

TargetSensor

TargetSensor

TargetSensor

Will detect any conductive material

Quoted distances are for mild steel

Sensor performance can be affected

by:-• Temperature

• Target material

• Target dimensions.

ON OFF

Target

Sensor

Oscillation Amplitude

Sensor output signal

d Properties

Sensor Installation

d Properties

Sensor Installation

d Properties

Sensor Installation

d Properties

Sensing Distance

d Properties

Sensor Wiring Systems - AC, DC , AC/DC Cylindrical Style

AC/DC 2-Wire

d Properties

N.O., N.C., N.O and N.C (complementary),

Programmable N.O./N.C

Output Configuration

Outputs may be Normally Open (NO) or Normally

Closed (NC) Some models feature both a Normally

Open (NO) and Normally Closed (NC) output which is

called a complementary output

Limit style Versa-Prox sensors feature a

programmable Normally Open (NO) and Normally

Closed (NC) output

d Properties

PNP or NPN Type

e Sensor Terminology

Series Installation of 3-Wire Sensors

+V

e Sensor Terminology

Parallel Installation of 3-Wire Sensors

e Sensor Terminology

Frequency or Speed

e Sensor Terminology

Connector Types

Pico

Micro

Mini

Cable Types Available:

– Pico Connector 8mm, 3 pin

– Micro Connector 12mm, 3 and 4 pin

– Mini Connector 25mm, 3 and 4 pin

e Sensor Terminology

Understanding Our Catalog

• Introduction (General Terminology)

• Theory of Operation

• Terminology

• Selection Guides

• Data Selection Pages

• Conversion Charts and Tables

Cylindrical Sensors

• Robotics

• Drugs and Cosmetics

• Metal Forming Machines

- linear prox senses different screw-head types

Equipment Monitoring

- prox senses broken drill bit

- digital or linear prox senses metal cap distance to determine absence/

presence of instructions

2.1.2 Magnetic Proximity Sensors

Magnetic Proximity Sensors

 Lets start with a permanent magnet.

through space.

magnet through which it interacts.

current through a coil

sources are identical - currents generate magnetic fields

a Principle

Equivalence between permanent magnet and coil

a Principle

 Relation between current and

magnetic flux density

current I and placed in a medium

magnitude of the magnetic flux

density is:

 r is the distance from the wire to the location

where the field is calculated

 the magnetic field is a vector and has a

direction (next) - field is perpendicular to I

B = 0r I

2  r

a Principle

b Construction

c Symbol

GND

Vcc

Output signal

Thường mở

Thường đóng

Công tắt hành trình điện truyền thống

d Properties

Connection

Indicator

Resonant circuit coil High frequency magnetic field

d Properties

Inductive principle of operation - but only reacts to magnetic fields

Interference from other magnetic fields must be avoided.

Solid state device - higher switching frequency - 1kHz

d Properties

Will detect any magnetic material

Sensor performance can be affected by:

• Temperature

• Target material

• Target dimensions

d Properties

PNP or NPN Type

e Sensor Terminology

2.1.3 Reed switch Sensors

Reed switch

Sensors

Thường mở

Thường đóng

Công tắt hành trình điện truyền thống

Reed switch

Công tắt hành trình điện truyền thống

Reed switch

Glass Tube filled

with nitrogen Reed contacts LED indicator

Reed switch

Reed switch

Reed switch

Reed switch

Reed switch

Interference from other magnetic fields must be avoided.

If positioned in mid stroke, switching point will vary depending

on direction of approach

Maximum current must be limited to avoid burning of the reed contacts

Reed switch

 Long life

drop

contamination

Reed switch

Advantages

 It is electronically noisy

Reed switch

Disadvantages

LOGO

tranhuutoan@iuh.edu.vn