Electrical and Electronic Measurements Proximity Sensors . Proximity

Electrical and Electronic Measurements Proximity Sensors   . Proximity

Electrical and Electronic Measurements Proximity Sensors . Proximity Sensors Proximity sensors detect the presence or absence of objects using electromagnetic fields, light, and sound. There are many types, each suited to specific applications and environments. Types of proximity sensors

1. Non-Contact Sensors : Optical Ultrasonic Inductive Capacitive 2. Contact Sensors (Mechanical)

2 Proximity Sensors 1. Optical (Photoelectric) proximity Sensors Photoelectric sensors are so versatile that they solve the bulk of problems All photoelectric sensors consist of a few of basic components: An emitter light source (Light Emitting Diode, Infra-red LED, laser diode), A photodiode or phototransistor receiver to detect emitted light, and

Supporting electronics designed to amplify the receiver signal. Photoelectric proximity Sensors Configurations: 1. Through-beam 2. Retro-reflective 3. Diffuse 3 Optical sensors (Through-beam) Transmitter

Receiver Optical sensors (Through-beam) Transmitter Receiver Optical sensors (Through-beam) Target

Transmitter Receiver Optical sensors (Through-beam) Transmitter Receiver Optical sensors (Through-beam)

Transmitter Receiver Optical sensors (Through-beam) Transmitter Receiver Optical sensors (Through-beam)

Transmitter Receiver Optical sensors (Through-beam) Transmitter Receiver Optical sensors (Through-beam)

Transmitter Receiver Optical sensors (Through-beam) Transmitter Receiver Optical sensors (Through-beam) Target

Transmitter Receiver Long sensing distance: up to 30 metres with some devices Will detect all but very transparent materials Must be accurately aligned Optical sensors (Retro-reflective) Type : Retro reflective

T Transmitter /Receiver R Reflector (prismatic) Optical sensors (Retro-reflective) Type : Retro reflective

T Transmitter /Receiver R Reflector (prismatic) Optical sensors (Retro-reflective)

Type : Retro reflective T Transmitter /Receiver R Reflector (prismatic)

Optical sensors (Retro-reflective) Type : Retro reflective Target T Transmitter /Receiver R

Reflector (prismatic) Optical sensors (Retro-reflective) Type : Retro reflective T Transmitter /Receiver R

Reflector (prismatic) Optical sensors (Retro-reflective) Type : Retro reflective T Transmitter /Receiver

R Reflector (prismatic) Optical sensors (Retro-reflective) Type : Retro reflective T Transmitter /Receiver

R Reflector (prismatic) Optical sensors (Retro-reflective) Type : Retro reflective T Transmitter

/Receiver R Reflector (prismatic) Optical sensors (Retro-reflective) Type : Retro reflective T

Transmitter /Receiver R Reflector (prismatic) Optical sensors (Retro-reflective) Type : Retro reflective T

Transmitter /Receiver R Reflector (prismatic) Optical sensors (Retro-reflective) Type : Retro reflective

T Transmitter /Receiver R Reflector (prismatic) Sensing distance : 1/2 to 1/3 of through-beam type Not suitable for reflective or transparent targets

Optical sensors (Diffuse) Target Type : Diffuse T Transmitter /Receiver R

Optical sensors (Diffuse) Type : Diffuse T Transmitter /Receiver R Optical sensors (Diffuse)

Type : Diffuse T Transmitter /Receiver R Optical sensors (Diffuse) Type : Diffuse

T Transmitter /Receiver R Optical sensors (Diffuse) Type : Diffuse T

Transmitter /Receiver R Optical sensors (Diffuse) Type : Diffuse T Transmitter /Receiver

R Optical sensors (Diffuse) Type : Diffuse T Transmitter /Receiver R

Sensing distance: much less than reflex type, actual distance depends on colour and reflective nature of the surface Larger targets result in longer sensing distances Not suitable for dirty environments Non-contact Proximity sensors Inductive proximity sensor Capacitive proximity sensor C2

S C1 P C3 Coil inductance increases as iron / steel object (S ) gets closer

Capacitance increases as metal object (P) gets closer because additional capacitance paths C2 & C3 are added and increase in value as the separation reduces. C1 is always present. 34 Non-contact Proximity sensors Ultrasonic (Sonar) sensors Ultrasonic sensor utilize the reflection of high frequency (20KHz) sound waves to detect parts or distances to the parts.

In general, ultrasonic sensors are the best choice for transparent targets. They can detect a sheet of transparent plastic film as easily as a wooden pallet. Different Colors has no effect The most common configurations are the same as in photoelectric sensing: through beam, retro-reflective, and diffuse versions. 35 Non-contact Proximity sensors Ultrasonic (Sonar) versus IR sensors The primary difference is that sonar has a wide detection cone and longer range

Unlike IR sensors, sonars are slightly harder to deal with when it comes to multiple sensors. Because of the wide cone, and how sound can reflect, they can interfere with each other quite easily. Typically, you must allow a 50ms between each firing of a sonar sensors, to let the ping die off. If you have multiple sensors, you can only ping one at a time, and must still obey this 50ms ring down time or have each sonar operating at a different sound 36 frequency

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