Module 4: Proximity Sensors

Eng. Asma Abu Baker

Outlines

• Analog Sensors • Digital Sensors • Proximity sensors • Inductive sensor • Capacitive sensor • Optical sensor • Ultrasonic sensor

Recap• Definition: senses the input physical variable

and converts it into a measurable signalSensor / transducer Name Physical variable Measurable signal

Proximity sensors1. Ultrasonic Sensor 2. Optical sensor

3. Inductive sensor 4. Capacitive sensor

Ultrasonic proximity sensor

• can detect solid, liquid, granular and powdery substances

Ultrasonic sensor application

• Detect the object within a specified range.• Detection range almost 100 cm

measure the distances of the nearby car

Detecting the presence of a person Detect the presence

of the car

Ultrasonic sensor application

Sensing Liquid Levels Control of lifting vehicles

Optical proximity sensors

• Optical proximity sensors are used for counting boxes, breakage and jam detection

Almost 10 cm detection range

Inductive proximity sensors

• Inductive proximity sensors are used to detect the presence of metals

• Detection range is very small.

Capacitive proximity sensors

• Capacitive proximity sensors are used to detect metallic and non-metallic objects such as wood, paper, liquid and so on.

• Detection range is very small.

Counting Application

Types of sensors

• Binary / Digital sensor (switches) – Output has two values only

• Analog sensors– Output has many values : Range

Temperature oC

Thermocouple output

25 oC 0.1 mv30oC 0.3 mv35 oC 0.6 mv40 oC 0.9 mv45 oC 1 mv50 oC 1.3 mv55 oC 1.5 mv

Does the thermocouple have only two values or many values ?

Many values, then its analog sensor

Temperature oC

RTD output

30 oC 0.114 kΩ35oC 0.116 kΩ40oC 0.118 kΩ45oC 0.12 kΩ50 oC 0.122 kΩ 55 oC 0.124 kΩ60 oC 0.125 kΩ

Does the RTD have only two values or many values ?

Many values, then its analog sensor

Temperature oC

Thermister output

k Ω25 1.430 1.135 0.9940 0.8245 0.750 0.655 0.51

Does the thermistor have only two values or many values ?

Many values, then its analog sensor

Binary sensors , optical sensor How many values I

am reading ?

Two values, then its binary sensor

Binary sensors, Optical sensor

Physical variable Measureable signal

Object exist 0 volts

Object don’t exist 24 volts

Analog sensors, Ultrasonic sensor

How many values I am reading ?

• Sensors can operate – by contact– Without contact (Proximity sensors )

• They are selected based on the application.

Is this sensor operates by contact, or without contact ?

Advantages of contactless proximity sensor

• Precise and automatic sensing of position.

• Contactless sensing protects objects from damage.

• Fast response, and do not include moving parts which can wear out.

Lab Activity 1

Don’t switch on the power supply till I check the circuit for you

Select Pulse

The clock is S2

Lab Activity 1

1. Connect Optical sensor

2. Connect inductive sensor

Conclusion

• Proximity sensors• Proximity sensors application • Analog and digital sensors