Inductive Proximity Sensors - Operating Principles and Applications

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Basic Features

Operating Principles
Model selection guide Application
Main Features Notes
Technical explanations Serial and parallel connection of sensors
Proper usage, installation and cautons

    

Basic Features

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Small dimensions

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High precision of repeated location

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Diversified exterior structures

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Good performance of anti-interference

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Many output forms

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High ON/OFF frequency

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Wide voltage range

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Dust proof, vibration proof, water proof and oil proof

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Short circuit protection and inverting connecting protection

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Long service life
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Operating Principles

Inductive proximity switch is composed of three parts: oscillator, switch circuit and magnified output circuit. The oscillator will generate alternating electric field. When metal object approaches this electric field and reaches the induction distance, whirlpool will generate in metal object, resulting in attenuation of oscillations and then stop them. The change and stop of oscillator is treated by behind stage magnified circuit and converted to switching signal, triggering driving control for non-contact detection.

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Model selection guide

No.

Composition

Code and definition

1

Switch category

LM:

Inductance type

        

2

Outward appearance code

□:cylinder type F: angular column type and plane installation type

3

Working voltage

30:

6~36VDC

310:

5~24VDC

320:

12~60VDC

20:

90~250VAC

210:

24~250VAC

220:

380VAc

4:

12~240VDC/24~240VAC

5:

Special voltage

    

4

Detection distance

01:

1mm

05:

5mm

10:

10mm

5

Output form

N:

three-wire DC NPN output

P:

three-wire DC PNP output

L:

two-wire DC output 

 □ :

two-wire AC output

W:

three-wire AC output

J:

Relay contact output

NP:

NPN+PNP double output

6

Output state

A:

Normally open (NO)

B:

Normally close (NC)

C:

Normally open + Normally close (NO+NC)

MU:

Voltage

MI:

Current

7

Subsidiary functions

T:

With aviation connector

Y:

Water proof, oil proof

I:

Special requirement

H:

High temperature resistance

R:

Ring type
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Application
Arm location detection of robot Bottle lid detection

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Main Features

Item

Explanation

Features
The size of detection object and detection distance

If the detection object is square metal sheet with constant thickness (t=1mm), detect at detection distance X when change its side length d mm.

 When the detected object is bigger than standard detected object, on the main, the detection distance is constant.
According to different machine type, sometimes the features will be different with that mentioned on the left.
To through type, the detection object is like cylinder metal bar.
The thickness of detected object and detection distance

Detect at detection distance X mm (front detector) when change the thickness of the assigned standard detected object 1 mm.

For more than 1 mm thick magnetic metal like iron, on the main, the detection distance will not change.
The effects resulted from the thickness of detected object and cladding material

Because the detection to standard detected object will be effected by its shape, size, material, and various cladding material, confirm through detection distance X mm measurement.

The effects resulted from detection distance and cladding material of the metal excluded iron will be different according to different machine type.

On the main, the machine type which detects all the metals will not ne effected by cladding material.
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Notes

About detected object

When the material of detected object is non magnetic metal, the distance of action should descend. But when the foil material is approximately thicker than a 01mm the detection distance will be the same as that of magnetic object.


If the film plating is extremely thin or non-conductive, detection can not be conducted.


The effect of cladding material. When detected object has cladding material, take note of the changing of detection distance.

About ambient weather


In order to maintain reliable action and long service life, please avoid the (outdoor) occasion beyond the stipulated ambient temperature. Do not drench it with water or water-soluble cutting lubricant when when it is used with cover, although the proximity sensor is waterproof. Do not use in the occasions with chemical agents, especially strong base, acid, nitric acid, hot strong sulfuric acid and so on.
About maintenance and overhaul

In order to keep the proximity sensor to work stably for long time, the following regular examinations should be performed just like general control.
 

1

Check the installation position of detected object and proximity sensor if any deviation, loosening or deformation exists.
 

2

Check the attached wires and connecting parts if any loosening, bad contact or wire breaking off exists.
 

3

Check if there is any metallic powder accumulation or not.
 

4

Check if the temperature condition and surrounding environment condition are normal or not.
 

5

Check if the detection distance is normal or not.

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DC switch should adopt insulation transformer and ensure stable voltage mains corrugation.

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If any electric power line or dynamic line passes through the surrounding of switch lead-wire, in order to prevent the switch from damage or error action, cover the metal bushing on the switch lead-wire and ground it to the earth.

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Set the switch use distance within the rated distance to avoid the effects from temperature and voltage.

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Wiring while power-on is strictly prohibited. Connecting the wires strictly according to the wiring diagram and output return elementary diagram.
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Technical explanations

Detection distance

Setting distance

Standard detected object

Move the detected object according to assigned method, the distance from the reference position (reference plane) to the detecting action (resetting)

Including the effects like temperature and voltage, without error action, the distance passed through from the practical detection surface to the objected object.

Take as standard detected object to detect the basic performance. The shape, size and material have been determined.

Differential distance

Response time

Response frequency

The absolute value of the distance difference between the distance to action and the distance to resetting

T1:

When the objected object enters the action zone, the time from proximity sensor being in action state to output appearance.
T2:

The time from leaving action zone to output disappearance.

Work out the tracking output times per second by repeatedly approaching the detected object.

Brief detection method sees the above diagram.
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Serial and parallel connection of sensors

Series connection of three-wire

DC and three-wire DC sensor

 Parallel connection of three-wire
DC and three-wire DC sensor		 Series connection of two-wire
AC sensor

Parallel connection of two-wire
AC sensor		 Series connection of machinery
switch and AC sensor		 Parallel connection of machinery
switch and AC sensor

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Proper usage, installation and cautons

Do not tighten with over-torque when mounting the switch. Adopt toothed washer when tightening.

When adopt adjusting screw, the tightening torque be within 2~4kgf/cm

When mounting the proximity switch on the metal part, do refer to the following diagram. Remain a certain space in advance according to the shown diagram so as to prevent the switch from error action.

Mount according to the size which is bigger than that in the following diagram to prevent the switch from error action resulted from mutual interference if mount the switches contra-positively or in parallel.

Adjustable switch action distance (sensitivity)

The action distance (sensitivity) of proximity switch can be adjusted by the means of trimming potentiometer. Increase the action distance and reduce sensitivity when turn clockwise. Vice versa. Do not use in the critical state of max. action distance.

Guard of switch lead-wire

When mount switch, fix the lead-wire at a distance about 10cm from the switch with wire clip so as to prevent the switch lead-wire from damage from outer force.

- DC switch should adopt insulation transformer and ensure stable voltage mains corrugation.

- If any electric power line or dynamic line passes through the surrounding of switch lead-wire, in order to prevent the switch from damage or error action, cover the metal bushing on the switch lead-wire and ground it to the earth.

- Set the switch use distance within the rated distance to avoid the effects from temperature and voltage.

- Wiring while power-on is strictly prohibited. Connecting the wires strictly according to the wiring diagram and output return elementary diagram.
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