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Measurements & Instrumentation
Module 4: Proximity Sensors
PREPARED BY
Academic Services Unit August 2013
© Institute of Applied Technology, 2013
ATE 314– Measurements & Instrumentation
Module 4: Proximity Sensors 2
Module 4: Proximity Sensors
Module Objectives Upon successful completion of this module, students should be able to:
1. Demonstrate understanding of the importance of sensors and the
function of proximity sensors.
2. Identify types of proximity sensors and their applications.
3. Demonstrate understanding of proximity sensor applications through
experiments.
Module Contents:
Topic Page No.
4.1 Introduction to Proximity Sensors 3
4.2 Proximity Sensor Applications 4
4.3 Lab Activity 1 8
4.4 Lab Activity 2 11
4.5 Review Exercise 14
4.6 Assignment 16
ATE 314– Measurements & Instrumentation
Module 4: Proximity Sensors 3
4.1 Introduction to Proximity Sensors
Sensors have increasingly become important components used to acquire
and transmit information in automated production systems. They are also
used in a number of other real world applications. Sensors can be divided,
according to the type of output signal, into binary sensors, also called
switches, and analog sensors. Binary sensors produce a digital output
(‘high’ or ‘low’), and analog sensors provide a varying or analog output.
Sensors are devices which can operate both by means of contact, or
without contact; they are selected based on the requirement of the
application. For example, the door at the entrance of the mall is equipped
with an ultrasonic sensor that senses the presence of people and enables
the door to open and close automatically (See Figure 4.1).
Figure 4.1: Sensor Application Example
In this module, you will learn about proximity sensors. Proximity sensors
detect whether or not an object is located or present at a certain position.
Sensors of this type operate electronically without contact.
Several advantages of contactless proximity sensors are given below:
• Precise and automatic sensing of position.
• Contactless sensing protects objects from damage.
• Fast response, and do not include moving parts which can wear out.
ATE 314– Measurements & Instrumentation
Module 4: Proximity Sensors 4
4.2 Proximity Sensor Applications
Different types of proximity sensors are used in many areas of the industry,
based on the application of position detection.
In this module, the following types of proximity sensors will be covered:
1. Ultrasonic Sensor
2. Optical sensor
3. Inductive sensor
4. Capacitive sensor
ATE 314– Measurements & Instrumentation
Module 4: Proximity Sensors 5
Ultrasonic sensors can detect solid, liquid, granular and powdery
substances; they are used in applications where it is required to detect the
object within a specified range. For example, an Ultrasonic sensor that is
embedded in the front and/or rear bumpers of the car, helps to measure
the distances to nearby objects at a low level. This provides
feedback/warning to the driver regarding the obstacle in the form of an
alarm, and thereby helps in preventing accidents.
Figure 4.2: Ultrasonic Sensor in Car
Other applications involve detecting the presence of a person and opening
a door, or, detecting the presence of a car in a car wash station.
Figure 4.3: Detecting a person Figure 4.4: Detecting a car at car wash
The figures below list the ultrasonic sensor applications in industrial
production and material handing processes:
Figure 4.5: Sensing Liquid Levels Figure 4.6: Control of lifting vehicles
ATE 314– Measurements & Instrumentation
Module 4: Proximity Sensors 6
Conduct Lab Activity 1
Optical proximity sensors are used for counting boxes, breakage and jam
detection etc. Inductive proximity sensors are used to detect the presence
of metals while Capacitive proximity sensors are used to detect metal and
even non-metallic objects such as wood, paper, liquid and so on. However,
the detection range of inductive and capacitive proximity sensors is very
small.
Counting Application: Different types of proximity sensors are used to
count the number of items produced in production lines based on the
material used in the application, as shown in the Figure 4.7 below.
Counting Cartons
Bottle Counting
Counting IC Chip Pins
Counting Packages
Figure 4.7: Counting Application Examples
ATE 314– Measurements & Instrumentation
Module 4: Proximity Sensors 7
Conduct Lab Activity 2 on Page 11
Detecting the presence of materials
Detecting the presence of materials/objects is very important in
automation industries.
Detecting Milk in cartons
Figure 4.8: Capacitive Sensor Application
Detecting Metallic Caps
Figure 4.9: Inductive Sensor Application
ATE 314– Measurements & Instrumentation
Module 4: Proximity Sensors 8
4.3 Lab Activity 1
Objective: To perform the counting application using an optical proximity
sensor.
Materials:
1. Power supply 24 VDC
2. Counting Unit
3. Multimeter,
4. Boxes/ bottles/any other
items to be counted
5. Optical sensor unit
(Festo: 167065)
Procedure:
1. Connect the 24 V socket of the power supply to the 24 V socket of
the counting unit and the RED wire of the optical sensor
2. Connect the 0 V socket of the power supply to the zero socket of
the counting unit and the BLUE wire of the Optical sensor
3. Connect the WHITE wire of the optical sensor to the clock socket of
the counting unit
4. Set the multimeter to measure voltage. Connect the COM probe of
the multimeter to the BLUE wire of the sensor and the red probe of
the multimeter to the WHITE wire of the optical sensor.
ATE 314– Measurements & Instrumentation
Module 4: Proximity Sensors 9
5. The following table summarizes the connections.
Power Supply Counting Unit Sensor wires Multimeter 24 V 24 V Red wire -
0 V 0 V Blue wire COM Probe
(Black)
- Clock socket White wire Voltage Probe
(RED)
6. Ensure that the toggle switch (No. 1) on the counting unit is set to
Imp.
7. Press start on the counting unit
No Description
1 Display Mode Switch
2 Start push button and
socket
3 Stop push button and socket
4 Clock socket
5 Voltage supply
(+24 VDC)
6 Digital display with four
digits
7 Reset push button and
socket
8 Voltage supply 0 VDC
9 Pulse output 100 pulses/s
10 Pulse output 1000 pulses/s
8. Measure the voltage output of the sensor before detecting any object.
Record your reading in Table 4.1.
ATE 314– Measurements & Instrumentation
Module 4: Proximity Sensors 10
9. Move the bottle near the optical sensor. What do you notice on the
counting unit display?
_____________________________________________________
___________________________________________________
10. Measure the voltage output of the sensor after detecting the first
bottle. Record your readings in Table 4.1.
Sensor output Voltage (before detecting the object)
Sensor output Voltage (once the object is detected)
Table 4.1
11. Move another bottle near the optical sensor and continue the
procedure.
Inference:
What do you understand from this experiment? List an application where
you think the optical sensor would be useful.
____________________________________________________________ _____________________________________________________ ____________________________________________________________ _____________________________________________________
ATE 314– Measurements & Instrumentation
Module 4: Proximity Sensors 11
4.4 Lab Activity 2
Objectives: To detect objects within a certain range using the ultrasonic
proximity sensor.
Material:
1. Power supply 24 VDC
2. Analog Ultrasonic sensor unit
(Festo: 177469)
3. Multimeter
4. Object under test
Procedure:
1. Connect the following circuit:
2. Set the Multimeter to measure current.
ATE 314– Measurements & Instrumentation
Module 4: Proximity Sensors 12
3. Move the object until it touches the sensor. Record the multimeter
current reading in Table 4.2.
4. Move the object 1 cm from the sensor and record the multimeter
reading in Table 4.2.
5. Repeat step 4 until the multimeter reading becomes constant (the
sensor cannot detect the object anymore)
Distance (cm) Sensor Output Reading (mA)
Table 4.2
ATE 314– Measurements & Instrumentation
Module 4: Proximity Sensors 13
Plot the characteristic curve of the sensor.
calculate the sensitivity of the curve.
_____________________________________________________
_____________________________________________________
_____________________________________________________
Inference:
What do you think is the range of the given ultrasonic sensor? Justify your
answer.
____________________________________________________________ _____________________________________________________ ____________________________________________________________
ATE 314– Measurements & Instrumentation
Module 4: Proximity Sensors 14
4.5 Review Exercise
1. What is the function of a proximity sensor?
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
2. What are the advantages of proximity sensors?
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
3. Mention three applications of proximity sensors:
1. ______________________________________________________
2. ______________________________________________________
3. ______________________________________________________
4. Indicate the proximity sensor that could be used in the following
application:
Detecting Metallic caps
_______________________
ATE 314– Measurements & Instrumentation
Module 4: Proximity Sensors 15
5. Write one difference between inductive and capacitive proximity sensors
Inductive sensor Capacitive sensor
6. Describe the sensor application in the following pictures:
Picture Application
ATE 314– Measurements & Instrumentation
Module 4: Proximity Sensors 16
4.6 Assignment
Visit your classroom blog that has been created by your instructor, and
complete the following two tasks:
Task-1: Sensor Application at your School
Identify one proximity sensor application at your school, and post your
views in the form of a message under the following questions in your
classroom blog:
1. Explain the sensor application to your peers
2. Share your thoughts on why you think this technology is helping your
school.
Task-2: Proximity sensors in your car
Identify two different types of proximity sensors that are used in your car
and post your views in the form of a message under the following questions
in your classroom blog:
1. Explain the first sensor application to your peers, and post your views
on why you think it is useful.
2. Explain the second sensor application to your peers, and post your
views on why you think it is useful.
3. Share your views on how you could improve this technology by using
additional sensors to make your car hi-tech!
ATE 314– Measurements & Instrumentation
Module 4: Proximity Sensors 17
Notes