Measurements & Instrumentation Module 4: Proximity...

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



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.



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



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



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



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



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.



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.



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.

____________________________________________________________ _____________________________________________________ ____________________________________________________________ _____________________________________________________



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.



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



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.

____________________________________________________________ _____________________________________________________ ____________________________________________________________



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

_______________________



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



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!



Notes

Measurements & Instrumentation Module 4: Proximity...

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