Photoelectric Sensors Operating Principles and Applications

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Operating Principles	Applications
Model selection guide	Technical terms
Characteristics and Reflection	Notes
Precautions and methods of preventing multiple interference
Connecting Sensors

Operating Principles

Photocell evaluate and respond to the light beam from the light source projector that is partially or completely obscured by object.

Light source and the receiver are on opposite sides. Object that passes between them breaks the beam and thus triggers the receiver. Hence the common name of a light switch

Diffusion reflective photocell is in itself an integrated source and a light receiver. The light emitted from the photocell is reflected from the object and returns the receiver to detect the object.

Feedback reflective photocell also has an integrated source and receiver. Reflective surface (mirror) reflect light to the receiver. When the object is between the photocell and the reflection of reflected light is reduced, changed, or diminishes, so the object is detected.

The working process of the photocell is similar to the principle of the direct reflection photocell (R2) with the remark that the beam of the light source is focused on a certain distance. The reflection occur when the object is exactly in the focus. The receiver responds and detect the object.

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Applications

Detection of cardboard

Bottles detection with or without labels

Counting products

Check failure on spinning

Validation of cigarette paper

Prevent entry into restricted area

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Model selection guide

No.

Composition

Code and definition

1

Basic form

G: infrared ray photoelectric switch (IC)

2

Outward appearance code

18, 50, 76, ...

3

Working voltage

2:

90-250VAC

3:

10-30VDC

4:

2-240VDC/24-240VAC

5:

Special voltage

4

Detection way

A:

Diffused

B:

Reflection

C:

Penetration type

D:

Marking detection

G:

Optical fiber

5

Detection distance

05:

5cm

10:

10cm

101:

10m

6

Output form

N:

three-wire DC NPN output

P:

three-wire DC PNP output

L:

two-wire AC output

J:

Relay contact output

S:

NPN+PNP double output

7

Output state

A:

Normally open (NO)

B:

Normally close (NC)

C:

Normally open + Normally close (NO+NC)

8

Subsidiary functions

T1:

Front delay

T2:

Rear delay

Y:

Anti oil type

T:

With aviation connector

I:

Special requirement

Example : G18 - 3A 10 NA

That indicates the infrared ray photoelectric switch of M18 cylinder, DC 10-30V working voltage, diffused reflection type, detection distance 10cm, and NPN normally open type.

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Technical terms

Term

Explanation

Term

Explanation

Optic axis of radiance

Standard detected object

That indicates the standard detected object, which is to determine the basic specifications in the reflection type sensor. Generally, it is white and lusterless. Use relevant detected object (for example, the slice) to the sensor for special purpose.

Detection axis

Min detected object

That indicates the smallest object, which can be detected by sensor under a certain condition. To correlation type and mirror reflection type, that indicates opaque body (wholly light sheltering). To reflection type, that indicates the corresponding value of iron wire or copper wire.

Detection distance

Correlation type
Stably set distance between light projector and photoreceptor

Repeted precision

That indicates the error of response position when repeating action under a certain condition.

Feedback reflection type
Standard setting distance between sensor and reflection mirror (omit “0” on the occasion with “0”)

Response time

That indicates the delayed time of outputting ON or OFF signal after the detected state changes.

Difused reflection type

The max stable detectable distance of object, generally white matt paper (omit "0" on the occasion with "0")

Intensity of illumination of operating environment (resistance to mixed astigmatism)

That indicates max, intensity of illumination, which doesn't result in error action, expressed by intensity of illumination of photoreceptor surface.

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Characteristics and Reflection

Technical Term

Explanation

Angle characteristic

To correlation type and feedback reflection type, move from right to the centering of left direction within each setting distance to gradually reduce the angle. That is shown by locus diagram of sensor action response angle (under max sensitivity state).

The characteristic of detected object size and detection distance

To reflection type, because the size of detected object affects detection distance, this diagram is useful to determine the stable detection distance according to the size of detected object. The sensor with sensitivity button is to turn the sensitivity to the relevant position of max. Detection distance where exactly detecting the standard detected object.

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Notes

To correlation type and feedback reflection type

The set distance should be less than the detection distance stipulated in the operation instruction. Because of keeping a room, although it can work when the set distance is bigger than the stipulated detection distance, the performance cannot be guaranteed. In addition, please make sure to keep certain room in the bad environment with rubbish and dust when setting a distance.

To diffused reflection type

The detection distance shown in the specification manual is in accordance with standard detected object. Actual detection distance will change in pace with the change of the size, color, surface evenness of detected object. Please ensure the stipulated room when set distance.

According to the change of detected object size and variation regulation of detection distance, bigger detected object, bigger reflection volume, longer detection distance. But when the size of optic receiving surface is bigger than the size of the detected object, the detection distance won't increase even if the object size increase again.

The difference between different detection distances of the detected object (Apply to scattered reflection type).

A

White matt paper (reference)

B

Natural color carton

C

Veneer

D

Black matt paper (grade 3 glossiness)

E

Glossy vener (Natural cream-colored board, brown propylene board, red ethylene synthetic board)

F

Gray ethylene synthetic board

G

Green glossy rubber board

H

Alboard

I

Reflector or reflecting board

J

Rusty iron bar φ10

K

Black cloth

L

Dark blue cloth

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Precautions and methods of preventing multiple interference

An unstable reaction is caused by an external light or from other sensor and this phenomenon is called multiple interferences.

●

Due to the cross-mounting receiver and transmitter

●

When using diffuse type in parallel you need to keep a minimum distance of 1.4 times the distance of detection

●

When using correlation type you need to keep a minimum distance of 0.4 times the distance of detection

●

The supply voltage must not be exceeded or decreased

●

Additional notes:

1.

dusty environment causes errors

2.

corrosive atmosphere causes errors

3.

splash of water or fluids, etc.., also causes errors

4.

Outdoor use and exposure to direct sunlight also affects the accuracy of the readings

When installing, consider the following draft

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Connecting Sensors

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