Detection based on “Light”
What is a fibre optic sensor?
Sensors come in a wide variety, and each type has strengths and weaknesses. This section provides a detailed look at fibre optic sensors.
Outline
The fibre optic sensor has an optical fibre connected to a light source to allow for detection in tight spaces or where a small profile is beneficial.
Principle and major types
The optical fibre consists of the core and the cladding, which have different refractive indexes. The light beam travels through the core by repeatedly bouncing off the wall of the cladding. The light beam, having passed through the fibre without any loss in light quantity, is dispersed at an angle of approximately 60° and emitted to the target.
The cores are divided into the following types:
Plastic type
The core of the plastic-fibre consists of one or more acrylic-resin fibres 0.25 to 1 mm in diameter, encased in a polyethylene sheath. Plastic fibres are light, cost-effective, and flexible which is why they are the most common type of fibre sensor.
Glass type
The glass-fibre consists of 10 to 100 µm diameter glass fibres encased in stainless steel tubing. This allows it to be used at high operating temperatures (350°C max.).
The optical fibre sensors are divided into two categories: thrubeam and reflective. The thrubeam type comprises a transmitter and a receiver. The reflective type, which is a single unit, is available in 3 types: parallel, coaxial, and separate. The 3 are based on the shape of the crosssection of the optical fibre.
Type | Description |
---|---|
Parallel |
Generally used for plastic fibres. |
Coaxial |
High-precision type, consisting of a core (transmitter) and surrounding area (receiver). The operating position can remain the same regardless of the direction from which the target enters the detecting area. |
Separate |
This type, containing several 10µm glass fibres in diameter, has separate areas for the transmitter and receiver. |
Type | Description |
---|---|
Parallel |
Generally used for plastic fibres. |
Coaxial |
High-precision type, consisting of a core (transmitter) and surrounding area (receiver). The operating position can remain the same regardless of the direction from which the target enters the detecting area. |
Separate |
This type, containing several 10µm glass fibres in diameter, has separate areas for the transmitter and receiver. |
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Detection based on “Light”
Method to choose photoelectric sensors as to environment
Photoelectric Sensors -
Detection based on “Light”
Features and advantages of fibre optic sensor
Fibre Optic Sensors